I use Dropbox every day. It just works. I don't need anything new from them, I'm perfectly fine with product that just works. Contrary to popular opinion, most people aren't 5-year-olds with short attention span, that constantly need something new to not get bored. They are busy people with little time to spare, and once they found something that works for them, they'd rather it keep working than search for something "new" that may or may not be useful for them.