I suspect that the target market wouldn't compare it with Dropbox, which gets expensive if you want lots of space. They were building something for serious photographers, with one of the mentioned pain points being the time it takes to backup a photo library. I understand this — I have about half a terabyte of photos (shot in RAW) and I don't take nearly as many photos as some.

That said, Backblaze works fine for me, although the initial backup did take a while.