We Americans are very paranoid about things we think are “too good to be true” (don’t know if that’s a phrase everywhere). This may be looking too deep into things, but I honestly think our country’s history of taking advantage of less informed peoples has influenced this - we know what happens when you take the bait, so it’s best to just accept the norm (ie paying your own metro fare) vs risk finding out what happens if they come back looking for what they “gave” you.

I actually sat and thought on this for a second. If someone walked up to me and tried to give me a $100 bill, I’d probably ask a few questions first, mainly, “what do you want?” If they seem genuine in that they just felt like being nice to someone (or even if I got the “social experiment” vibes), I’d probably take it, and ask if I could buy them something small with it (like, if this were outside the grocery store, ask if they wanted some snacks or a drink or something).

I think if I were in a group setting, someone approaching the group trying to give us a $100 bill would probably would be quickly closed out of the circle, and everyone would get quiet and look away until they left, at which point everyone would talk about that weird guy trying to sell us something.