FWIW, my son worked at a salad/soup buffet restaurant during his first year of college, and found that only 2-3 tables during dinner time would tip, usually $1-$2, for about $8 per person meals aside from drinks. Believe he said he once got $5 from a big table of 12.

Another comment regards a previous comment in the earlier post:

"Learn from Singaporeans where tips are politely returned."

I've been to Singapore many times, and do not tip in restaurants where a 10% service charge is on the bill, which is most of them. On the other hand, when I have tipped, it has never been declined by taxi drivers, bellmen, or restaurant staff. Still it is true that tips are not expected in Sinagpore.