When I flew standby/duty as a staffer I'd always bring something for the crew. No hidden agendas, no desires to be "bumped up" (especially as I either already had F priority or flew on flights with only Club), just to give something back. From speaking to my wife, whenever they get some presents it's normally from fellow airline employees or at Christmas and it's in good nature.

She once had a very creepy experience with a man in F who wanted to buy her something from the duty free. He was extremely insistent, she kept on refusing (she had some bad vibes about him) and deflected him to a donation to Flying Start. Eventually he started harassing her on LinkedIn and stopped only when she threatened to contact his employer.