Boo Boo Too,
American tip-craziness probably has a lot of different roots. The whole American Dream is the idea that every one of us can make money and elevate themselves, no matter how humble or lowly their current position. I think underlying that, then, is the idea that workers have a "right" to put out a jar, as uncomely as it may seem.
We also have a very different social welfare system all around from the UK and most of Europe. Our minimum wage is well below the poverty level, and the "safety net" has a lot more holes in it than in the UK. And wealth disparity, the gap between the rich and the poor, is quite high in the US.
I'm NOT making a political statement or advocating any position. I'm simply pointing out that non-apparent circumstances can sometimes dictate differences of behavior in seemingly familiar situations. This is true, of course, whenever travelling to any foreign country.
I, too, find it rude when hotel employees in particular dig for tips. Maybe, though, it is a uniquely American trait to be cold hearted and just treat this like any business transaction. But then, I'll always remember how hard it was for me to make ends meet when I was waiting tables and carrying luggage, and how challenging it really was to provide consistently good service. I enjoyed the challenge, but realized that if I had a bad day at work (distracted by something personal, under the weather) I could lose 50% of my income for the day. So usually, I just dig in and hand over a tip.
Here's one thing I do: I go to a bank and get some $2 bills and $1 gold coins. The uniqueness of this tender inflates their value. If I tip a with a two, the look on the recipient's face is often similar to if I had just handed over a fiver.
Meanwhile, if you're interested in learning more about wage and welfare issues in the US,
http://www.epinet.org/ is one place to start, though they have a generally liberal agenda. And, of course, those on the right have some very different opinions at
http://www.epionline.org/.