The trend from "tip" to "service charge" is one you will see spread further in the USA.

For one, a tip belongs to the waiter. The employer cannot legaly alter the amount he or she pays to the employee - usually same or next day.

With a service charge this is not the case, and the restaurateur can decide to allocate a portion to the rest fo the crew, hold on to it for a week or a month, etc. I do believe, however, this now becomes part of income and now social security, etc. is paid on the full payout of wages including this "tip".

With tax laws in effect since the mid '80s it makes sense for a restaurant to do this as the burden of withholding on tips is with the employer.

If the service is exceptional, I always have a few extra dollars in cash to discretely hand to the waiter / waitress. I doubt the employer will tyr to pry it out of his / her hands!.