What are the 30's people using it for?
Paying off a bet about who would become CEO of twitter
Paying someone for my portion of a bar tab.
Fantasy Football league dues
Receiving money from someone for their portion of a bar tab
Paying someone for movie ticketsEven though I have had paypal for years, most people cringe when someone doesn't yet have Venmo and offers to send via paypal.
I think the reason why I never heard of it is cause of the way my friends and I handle money. One person will grab drinks one day and the next time the next person picks up lunch. If someone buys a pizza everyone just gives them whatever bill from their pocket. None of us really "keep track" in specific dollar figures. Nobody says "this is only $5, you owe me $6."
Of course this kind of thing doesn't work out for every group.