But, on the other hand, I just heard a headline about a survey on news radio yesterday, that said that 2/3 of the population surveyed now have a negative attitude toward tipping, which is much higher than previous surveys.
I didn't hear any proposed reasons for why this is, but I would wager that all the complaints in this thread have a lot to do with it.
So, IMO, the reason for "why not?" is that this continuous begging-for-unnecessary-tips may end-up backfiring, if more and more people start to experience "tip exhaustion" and start giving less and less tips overall.