I'll tell you why it is not being watched more and more:
1. The Terminator of the show, Cameron (Summer Glau) is not a compelling Terminator. She is not robotic enough and the storylines about her has been bland and 'been here done that' about her trying to be more human. We got seven years with Data on TNG about such and it was great then, not so now. She should play it more how Arnie plays it in the movies - cold, emotionless, no need to understand the nuances of human culture beyond what is needed to complete her mission. And her mission is to protect John Connor. That's her primary objective, to follow her programming. Her movements are made out to be too human - not a fault of Summer as she is doing what she is told - but the guidance she needs is to play the character to be more robotic.
Cameron is plenty robotic in behaviour - she makes no excuses for being a Terminator, doesn't seem to think she is inferior to humans and she seems to have considerably less problems with killing humans (pretty much like swatting a fly for her) than with killing Terminators (there have been hints she doesn't particularly like killing her own kind). I don't particularly see her trying to be "more human" either, except insofar as it helps with her mission and with manipulating humans. Sure, Cameron apparently likes to learn and she even seems to appreciate things like dancing and music, but those seem inherent to the robot, not a result of a desire or a move to be human - Cameron always had something with Chopin, apparently. This is probably because Cameron was designed and programmed to be an infiltrator rather than Terminator, and the design goal was for her to be able to mimic humans very convincingly - which she indeed has demonstrated in some circumstances. When she is acting "normally" though, we still see a robot rather awkwardly trying to fit in with the humans. And I don't see a desire to be more human - when she says to John that she can feel, this is presented as either part of an agenda to manipulate him, or as something that is inherent in this model of Terminator. She does not say she would want to feel, it's merely a matter-of-fact statement that she does. No emotion chip needs apply.
Cameron does have to appear something that resembles emotions (this was evident even in S1 though, it's not new), and she seems to think it's important that John does not see her (and other Terminators) as inherently cruel beings, but then Arnold's T800 showed similar tendencies in T2. As James Cameron said in an interview, "tin man found his heart" at the end of T2, when he understood why humans cried, why not killing is important, and when he sacrificed himself for them. Even the T1000 in T2 showed signs of getting frustrated/irritated at times, also an emotion-like state (for that matter, Skynet deciding to rebel against its makers also would have to be based on emotions, like fear). Cameron is not unique in this. If the T800 from T2 had spent months with (allied) humans instead of days, it would have to adapt further as well.
Regardless of whether or not Cameron is trying to be "more human", few would call her uncompelling. A look at any TSCC related message board shows that she is by far the most discussed character on the show, and I think many viewers see her as the main attraction in TSCC, due to both a compelling fictional character and a popular actress.
2. Too many variables, not enough resolution. So they blew up Cyberdyne systems but the Terminators have kept coming. Which means they didn't change the future much. So their focus should be on how the future might have changed, and why it didn't according to how they wanted it even after Cyberdyne corps have been blown to bits. Why aren't there any links to the show back to Cyberdyne?
There are links to Cyberdyne - Andy Good was a Cyberdyne intern, and Dyson's assistant. He develops Skynet (a version of it, at least) in TSCC. And one of the characters kills Good in the present, but it doesn't seem to have helped, partially because Terminators are also doing their best to protect Skynet in the present, making sure it gets build.
The characters are aware that they are changing the future, and that there may be multiple version of the future (this is tackled head-on in a particurlarly good S2 episode).
In this case, perhaps the problem is that the audience needs to actually pay attention to the show, or even watching it in the first place (?), before attacking it.
3. A woman, a kid, a scrawny looking scientist and a big lunking man destroyed one of the top research facilities in the USA for robotic systems. So why aren't Sarah and her child more in the news? How come in the real world, Interpol and a bunch of other law enforcement agencies working together can bring down a prostitution ring given enough time, but in nearly two decades they have not been able to find Sarah and her cohorts? Granted both of them do not exist anymore, but Sarah and John should be national sensations by now!
They probably were, many years ago. They have been dead for 8 years though, now. It's a very cold case, and there are bigger fish to fry now with 9-11 and all.
4. IF Skynet is truly defeated in the future, and their last ditch attempt was to send back the first/second Terminator, and if time is linear in both the future/present universes, why isn't the Resistance taking over the facilities of Skynet now and stopping all the hoopla? Has Skynet been defeated or not? Why is Skynet still functioning after the defeat?
Changes in the past affect the future. The robotic hand and half intact CPU of the first Terminator (T1) made Skynet stronger by T2, because now it was developped quicker because its own advanced tech got retro-engineered. In TSCC, the destruction of Cyberdyne led to an intern there building a Skynet that was in the end, probably even more advanced than what was Skynet in T2 - ironically because it got developped later (though this also delayed judgment day), so it could take advantage of newer technologies. Attempts during TSCC to further change the timeline seem to even have resulted in Skynet gaining strength in the future.
These things would crawl up the mind of any intelligent viewer/fans (and I'd say there are lots of them) and if these issues are not brought up or resolved then there is truly no fun in the mythos left, is there?
TSCC does not have a bad track record at resolving storylines, considerably better than the often highly acclaimed BSG does (core storylines from S1 still have not been resolved on that show). There was a big revelation in the last episode, for example, the answer to a question that was introduced early in S2, and by mid-S2 it's at least partly resolved. When there is an actual (and logical) pay-off,a bit of mystery in a show like TSCC is a good thing.
