I can't speak for the other poster, but in my case gentler learning curve (I've been using vim for about 10 years and I still don't know 10% of what it can do), smooth scrolling, a real GUI (vim's text menus can be pretty confusing at times), and the features vim didn't have at the time like multiple cursors, command palette and go to anything.
Why do I keep using it? Because generally new functionality requires about 2 minutes of readme.md and then it is working, rather than half an hour of hacking with vim config files.
Overtime I just found myself being more productive and 'happier' while using Sublime. A lot of that comes from the extra functionality it offers (built-in and from numerous plugins). Eg, Markdown preview, image preview, color picker, various project search and management features from SidebarEnhancements.
I still love Vim and use it for editing single files or whenever I remote in to another machine but this new generation of text editor / IDE hybrids just fit my project workflow a bit better.
I'd say there's always room for a product that works well. Textmate, back in the day, had to come in and compete with well-regarded software after all -- even if we ignore vim/emacs as being insufficiently-Mac, there was BBEdit.
I don't know that I'd say Sublime users are "stuck". The long beta on v3 seems to be splitting the community, somewhat, but it wouldn't be surprising if the final release resulted in it consolidating again.
Perhaps, but either way as a ST2 user I'm looking for a replacement and once ST2 does not meet my needs I'll either go back to emacs full time or look towards something else for light weight stuff.
I've already movers most of my we stuff to IntelliJ/WebStorm. I really liked ST2 but was a little miffed that right after I bought my licence ST3 was pushed to the forefront of the site without a reasonable upgrade plan.
I do certainly agree that the new-version / upgrade thing has been poorly handled. If nothing else, announcing it and causing the split should have been followed by rapid development instead of over a year of slow beta releases.
Text editors are dime a dozen and in that space, you are competing with much more than tools that are geared just toward developers.