Agree but things have been moving away from niche channels even on cable. We used to have court TV, The Nashville Network, and so forth but they all either rebranced or just became something like "TNN" which didn't stand for anything. That s how we get wrestling on SyFy. The trend for a while has been channels moving to be more generalized and less specilized. On streaming, I think you are hitting the fact most people are saying they are going to only pay for 2-3 streaming services. If that is what users want they are only going to sub to services with lots of different content and not use one of those slots for a real niche channel. We do have some niche services like WWE Network, DC Universe (though that may get pulled into warner's service) but the niche of the niche which was stargate command just shut down. I'm not sure the market really wanted extremely niche streaming services. I think what is needed is a streaming aggregator. You pay a bill to one company and select which services you want (yeah would be kinda like odl cable packges) but you only have one bill to one company. Also what would be required is a UNIFIED GUIDE. That is my biggest gripe on streaming - figuring out what show is on what service. If I am subed to 4 services I want to be able to just search for "friends" and then get directed to the correct service without me needing to know.
The reasons this happened had more to do with advertising than anything. Basically while we would look at SyFy as specializing in SF/fantasy, advertisers looked at it as a station watched by young males. The tail wagged the dog, and they pushed for more content liked by males in the same age band, hence wrestling. Since most of the major streaming networks do not have commercials, there is not the same pressure here. The market will accept niche streaming at a low enough price - or with the right content. Things like Kickstarter show you can raise a lot of capital from a small but loyal fanbase.
We will see but I'm not so sure. We've seen on here a ton of I'm not paying for another service for one show comments.
This site does a pretty good job at keeping track of what shows are available on what service. It works for movies too. https://www.justwatch.com/us/home