How is it different to a cover charge at a night club for example? So if you went to a night club, you woudn't tip at the bar now?
You said specifically that the tip is "to show your appreciation not just for the person who serves the beer, but for the experience of being at a place that is upscale enough to deserve charging $7 per beer."
So you don't appreciate the person who served you at the ballpark? Is a ballgame not a unique experience and upscale enough considering they are able to charge you $x for a beer? Besides the price of the ticket more or less goes to the owner of the club, the players, or the association in royalties(mlb, nfl, etc). I don't see how you can ignore one place just because you paid a price of a ticket to watch a game unrelated to the person who served you who in fact probably make a lot less than a barmaid does because you DON'T tip them.