That's pretty much what has happened in EQ2. Of the "Featured" interfaces, they're all either currently maintained by a new author or shut down (or in the case of Drums, going to shut down). The game's been out a long time, people move on and often there's someone who wants to try and keep their preferred UI going.
As for some windows in Fetish now being the default layout, there's usually enough hard-coding behind them (Character window, marketplace, etc.) that they can only be changed so much to start. Honestly I can think of no major feature that I'd otherwise include in any window that's left using the default layout, so just tweaking things like spacing doesn't become worth the hassle to me or to the users, who have to rollback to default and wait for a patch whenever SOE decides to randomly change the window anyway.
In times past, major UI changes were kept mainly in the monthly or quarterly (GU) patch cycles, with usually at least some time on the Test server for maintainers to update their UIs in advance. That hasn't been the case the past year+, now they make changes in regular weekly hotfixes that utterly break custom UIs (crash bugs at the worst, just loss of functionality at best). When it comes to those windows the risk vs reward for making small modifications to them just doesn't add up for me; I'd rather take the more future-proofed route that means less work for me and fewer issues for folks that use the UI, all at essentially little to no loss in form or function.