Perhaps I dont fully understand the value of something like DropBox, when it comes to syncing my files the only thing I've ever needed has been github (or other online repo). Among syncing it has all the other version control goodness, and I will likely use it until I can setup some kind of home server
I work remotely with my colleagues. We constantly are doing stuff like creating/updating excel files and all sorts of other stuff that has nothing to do with source code.
With dropbox (or equivalents) I update something in the file, and it's updated right away everywhere no matter where my co-workers are.
Dropbox also has good enough built-in version history (especially on business), it will keep the changes of any file for like 6 months. So if I want to look how this excel file looked an hour ago, I just click "version history" and it pulls up all the different files and I can restore any one.
So for people who work remotely and just want to sync files / have some ability to restore previous versions dropbox is a life changer.
Yeah, of course this could all be setup to have each person on a VPN and using a shared folder on a server where we are logged into the domain or we setup a ZFS filesystem which takes snapshots and I can restore etc etc. In a small company, F that. I've done all that bullshit, it isn't worth the time and maintenance when you just want a damn synced filesystem among co-workers.
So there is the value proposition!