Originally Posted by
1worldFlyer
How is that different from tipping a bar tender though? That's just as much a bribe in exchange for preferential treatment and/or larger servings of alcohol per drink as tipping an agent in exchange for the benefits you listed.
In the US, tipping someone who serves you food (waiter, bartender, etc.) is customary. For better or worse, it is part of the culture. Tipping a Gate Agent is not part of our culture and, even if it isn't intended to be so, can be constituted as a bribe for better treatment that violates the airline's policies.