Venmo's instant transfers are no longer limited to sending money to debit cards. The PayPal-owned service now permits transferring money immediately to linked bank accounts. It still incurs the same 1 percent fee with a minimum 25-cent transfer cost and a maximum $10 outlay. If you can tolerate that, though, it might just save your hide if you're running low on funds or just want assurances that money is sitting in your bank account.
This should be generally available in the "coming weeks," and free bank transfers are still available if you're willing to wait the customary one to three business days. There's certainly no mystery as to the strategy here. Venmo is betting that there will be enough of an urgent need for cash (or at least, enough impatient people) that it can make a profit from an otherwise free service.