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.
Developers will pay decent money for any editor that helps them create better code (and thus more money). :-P