You can also take money from a bank account using an account number and routing number. That's why Donald Knuth stopped sending out checks to pay bounties.[1]

Is it another startup whose usefulness stems in a large part from the lack of ubiquitous free, same-day interbank payments between checking accounts in the US (unlike much of the rest of the developed world)?

Partly but not all.

[1] http://en.wikipedia.org/wiki/Knuth_reward_check