Tipping flight attendants?

Why don’t people do it? Should we start? I think I’ll start. Pros: they are absurdly underpaid & this would help; airlines would not have to pay them as much; flights would be more pleasant with better service… Cons: costs a couple more bucks a flight; sucks for people who can’t afford a couple more bucks a flight; there’s gotta be some mess with the even distribution of tips among attendants…