My gut feeling is that whether you are familiar with the popular cash sharing apps really depends on your social circle. Among young people/students etc, not surprisingly I see a TON of Venmo users. Among adults with steady reasonable paying jobs, not so much. I've seen Venmo reguarly used as a Verb in social media too.

I know for me personally I'm far more likely to say "you get it next time" than bill my friends for some share of an outing. If it's sufficiently expensive that this doesn't make sense I'd just split the check. If I was younger and still a student I can absolutely see the appeal though.

Me neither. I googled it, out of curiosity myself. I was confusing it with BevMo, a retail chain for beverages et al.