You say that, but then stuff like OnePass and Dropbox decide to reneg their subscription services down-the-line or simply make their clients worse. A lot of the time, a subscription to a program gives the developer no incentive to iterate on what already exists.
And then you just drop them for a competitor. Since you have no sunk costs, you lose nothing by hopping to whatever the best option is other than a small amount of pain migrating, But for something like dropbox, there isn't that much lock in.
I've never heard of OnePass so I have no idea, but Dropbox is very easy to replace. I'm also not even sure how you'd expect a "pay once" model to work for cloud storage.
