You seem to be implying that people who use Venmo and/or prefer to deal in exact numbers aren't decent human beings. I suggest you reevaluate that position and consider how greed might not be the root cause of someone behaving that way.

I'd also argue that using a Venmo doesn't take away the opportunity for someone to be generous. Venmo isn't much different from cash except that it makes it more convenient to be precise - it certainly doesn't force anyone to be precise though.