Anecdotally, it's rampant. To the point where crews will take bags(!) of booze and certain snacks off planes for layovers / gifts etc.

And I didn't mean you should bring candy for the FA's solely in expectation of getting something in return. You should really do it because they work surprisingly stressful jobs with absurd hours. They often have to deal with the worst kind of people and could really use a metaphorical hug every once in a while.

Source: Dated a FA for a long time. Know many others.