tipping

A while ago I heard a guy from some restaurant group talking on the radio about the current situation with tipping prompts everywhere.
He explained that generally a tip is left in recognition of the good service you recieve. He said now let's imagine 2 couples going into a restaurant, sitting at 2 separate tables. One couple orders a $20 bottle of wine, the server brings it, opens & pours it. The second couple orders a $100 bottle of wine, the server brings it, opens & pours it.
So going with your 20%, the first couple leaves a $4 tip. The second couple leaves a $20 tip. Why? The service was exactly the same in each case.
He argued that basing tips on a percentage should not be done. It simply encourages inflated prices to reap bigger tips, particularly where staff is underpaid.
On another note, a friend of mine walks into a restaurant with a 15% tip to start, then depending on service, the amount can go up or down according to the experience.