It's been a long time battle for American restaurant staffers to extract tips from certain foreign tourists. We know they know our culture before even leaving their own countries. Most of them, anyway. But still it seems that a lof of them come here and play the un-savvy traveler role with their servers. We feel that if you can afford, financially, to travel to another country, then you can afford to tip in bars and restaurants. Why don't they, then? Well, most tell me that they don't see why they should tip. I guess the answer to that is: for the same reason why, when asked for directions to Radio City Music Hall, a server doesn't direct these unsuspecting tourists to the south Bronx... because we have a conscience. We should look out for strangers, even if just on a human level. If you have an inkling of what a server does to earn their tips you'd gladly fork over the 20%. If you don't, then I suggest you read Why Tip the Waiter.
Aside from that though, there are other reasons. I know a lot of English tourists for example come here to shop for clothing simply because it's much more expensive to buy back home. It's actually cheaper to fly here to shop and probably eat and sleep, as well. My point is that currently $15 American dollars is equivalent to €10.23. If some tourists are saving money overall by coming here then it shouldn't be much of a big deal to shell out a few more converted euros to leave as a tip.
Another reason is that if every foreign tourist who came here left a tip everywhere they went to eat or drink that would put billions of dollars back into our economy, which if you haven't noticed isn't doing so well these days.
Lastly, when anyone, foreigner or local alike, doesn't tip a server or bartender at all, the waiter actually ends up paying for the customer to be in the restaurant out of his own pocket. How is that you ask? Our government looks at the amount of money each waiter or bartender rings into the computer every shift, then assumes the percentage of that they made in tips. When they aren't tipped the government is still taxing them on assumed tips on that check whether they received a tip or not.
I feel that tipping is our culture here in America. When traveling abroad I'm expected to abide by the cultures of wherever I'm traveling to. You can be damn sure that I'm going to research them and feel embarrassed if I'm told later that I've insulted a local by taking part in something that's counter to their system of operation. That's just me, though. I'm sure there are still some that just don't care either way, and hey... that's fine. If we're going to live in societies like that, however, then it's every man for himself when traveling. Don't ask me for directions or advice to make your stay in this country any more convienient. Spend that money that you didn't leave as a tip on the second taxicab you're going to have to get when you "accidentally" end up 15 blocks north of Yankee Stadium in December at 3AM when no one cares enough to look out for you on a human level. I'd rather we just didn't go there.