My standard is $1 per beer/drink bartender hands me. An airport bartending job is a tough gig. It's not like you can park next to the back door of the bar and walk in to the job. It's a bit disappointing to me when I see cheapskates stiff ($0 tip) wage+tip people who are making their travel somewhat more pleasant. An airport bartender is different than an airport Starbucks employee. Starbucks employees are not depending on tips just to get to the "normal" wage. Yeah - when I see tip jars where employers are already paying $15/hr, I am a bit annoyed. There's no tip cups on UC bar counters, but that's where the tips ought to be tendered. I'll go an extra buck if bartender is genuinely friendly and displays some skill/knowledge. The LAS bartenders are usually the best I run into.

As for the showers - I don't think the attendants are on a wage/tip scheme - they're probably getting more than minimum wage and just taking advantage of the expanding tip culture. I'm not helping the expansion.