Maybe it's a regional thing? Almost no-one here uses Venmo. I mentioned it around my friends the other day and they'd never even heard of it. 2-3 people at my office use it semi-regularly but that's how they are--trying out almost any new app for anything. For all I know they've dropped it and are on to something else now.

If I tried to pay anyone with it I can guarantee they'd say (a more polite version of) "WTF is that? No. Do you have money? Try money."