Oh, come on. It's got nothing to do with lack of care or devotion. It's got to do with recognizing that the kind of slavish rigidity you're advocating is not actually good writing. It takes more care and devotion to understand when to stay true to past continuity and when to be more flexible than it does to just mindlessly, mechanistically adhere to every last trivial detail, even the ones that get in the way of your story.
The thing is, no work springs complete from the creator's head like Athena out of Zeus. It's the end product of a lengthy process of development and evolution, with ideas being tested, discarded, modified, revised, reconsidered, rearranged, etc. So what the fan sees as a fixed, monolithic work is really just a cross-section of the entire process of creation that the writer perceives. The writer doesn't care any less about the work; the writer just sees it more as a fluid, evolving entity rather than a frozen image carved in stone. So a writer's willingness to revise a work is a continuation of the same process of revision and editing that led to its creation in the first place. One of the most important parts of the creative process is editing, cutting out the bits that don't serve the story. First drafts are usually rough; it's the editing that makes them good, or not. So removing or changing the parts that don't fit is part of what makes the story work in the first place -- like bonsai. From a creator's standpoint, disregarding or retconning some old bit of continuity isn't neglect or contempt for the work -- it's just editing after the fact. It's trimming the bonsai.
Hear hear!!! I've written a bunch of little things over the years... just a hobby mind you, nothing professional. I've decided to actually buckle down and write a novel and now that I'm doing it, I can totally see the truth of this!
... Does it have continuity? I'd say yes in the larger sense it does. The sweeping arc of all five shows do add up to a collected whole, but to muck it all down for the sake of not bumping into an extremely minor throw away statement.. usually involving a not-so-well-thought-out figure to begin with is sort of sacrificing the story for the silly side bits.
That said, even with all the internal contradictions, Star Trek
still holds as much or more water as a fictional setting than do many "based a true story" films and biopics which really do have homework to do. Even those writers usually chose to cherry pick the facts in service of the story they want to tell. This is just how it's done...