Canon is only part of it. A succesful franchise is a set of pieces that all fit together - the same characters, the same backstory, the same style (which doesn't necessarily exclude live-action and animated shows), etc. Fans of that franchise like it the way it is. Once Hollyweird starts making ill-fitting changes, the new "version" is obviously no longer part of the same franchise ... so since it's not part of the same franchise, and in most cases the people making it even say it's a different show, why re-use the original name??
Names are given to things for a reason - it's distinguishes them from other different things. Re-using the same name for a different version simply makes a confused mess of the franchise. If I say "Battlestar Galactica", you have no idea which version I'm talking about.
It makes absolutely no sense at all.
Re-using the original name also brings along a pile of baggage and expectations. If they simply and sensibly give their new "version" a new name, there wouldn't be any of that. For example, if someone didn't like the original "Battlestar Galactica", why on Earth would they stupidly watch something else called "Battlestar Galactica"? Why are they suddenly expecting it to be different? If it was called "Warship Gigantica" or whatever, then it has none of that expectation.
One reason they re-use the original name is simply to extend the copyright and stop (or at least make it difficult) other people making a proper version. It will probably never actually happen, but Glen Larsen, for example, is planning a proper "Battlestar Galactica" movie that does fit with his original TV series - he apparently owns the rights to movie versions, but not TV versions. (On an even sillier note, there is someone else also planning a "Battlestar Galactica" movie that they claim somehow fits with both "versions". :rolleyes:)
If you're going to re-use the same name simply because it's vaguely similar, then we may as well not bother with different names at all. Why not call all human males "Bob" - they're all male, all (usually) have two ears, two eyes, etc., so obviously they're all "the same".
Then there's the moral issue. Why does some young idiot in Hollyweird think they know better than the person who actually created the original? The only person who morally should be allowed to make changes to their franchise is the person who created it (or if they're dead, a custodian person) ... that doesn't mean new stories can't be added, just that they have to pass by the custodian and there can't be silly changes to what has been established.
If something is no longer "good enough" for Hollyweird, then let it go and actually create a new franchise, rather than butchering and splintering the old ones.
![Sad :(](./images/smilies/sad.gif)
There's thousdands of book series that have "gone out of fashion" but are still loved by the fans of them ... you (usually) don't see them being stupidly "rebooted" under the same name.