I never thought not tipping in US is an insult. For restaruant I will tip no matter what unless really bad service. I could still remember one time I went to a restaurant with a friend, the waitress not busy at all just keep talking to other waiters. We ordered appetizer and entree, while we were already eating entree, then we asked about where is our appetizer, she said she didn't put it for the order. So we decided not to tip at all, who knows the manager follow us out of the restaurant when we leave and ask for the tip. We told him our server did a poor job, it is an insult to me and my friend.

There was also another occasion, and it happened in Westin New York, for breakfast in the restaurant. There were about 5 tables of people. Sit down, menus take forever to come, then take forever for someone to come to ask for my choice, note there were actually 6 waiter in total. Every one of them try to ignore all tables, try to pretend to be busy. I saw a lady on another table ask for a glass of water, it took her to ask for 3 times finally get her water for more than 10 minutes. The restaurant is also rather tiny also.

So with those incidences, why should someone still tip ?

For all other business, good service with tip, standard service no tip.