I'm a 35 year founder of a small company in San Francisco. I had never heard of Venmo until recently. The dividing line among my team is around 30 years old. Below 30 -> use Venmo all the time. Above 30 -> never heard of it.
This may vary by your group and where they at in life, but by my late 20s, those things mattered a lot less. If I buy someone a beer, I just hope they will get me back at some point and if not, then I bought them a beer- no big deal-enjoy! (well enjoy, unless this is the fifth time in a row I have done this and you haven't gotten me back).
I am in my mid-late 30s, and I have Venmo. I just tend to not use it very often, only for fairly big ticket items- concert/event tickets, someone buys a gift for someone else that we all chip in on, a restaurant gives a hard time about taking multiple credit cards, etc.
I much prefer it for payments amongst friends than anything else now though. It’s rather good.
I would love to know if the college crowd was a specific target for venmo: it’s nailed it