The new Tipping standard

To be honest I can’t remember when this new 20% tipping rule started for us.  It kind of just happened.  For some reason the question popped into my head today “Why did the new Tipping % increase?”
It can’t be because cost of living has increased and the wait staff incomes need to increase with it.  Cost of living increase is reflected in prices on the menu.  Since tip is a percentage of the bill the increase is also reflected in tips.

There hasn’t been any significant change in the level of service that warrants a increase in the percentage.

I’m not begrudging the increase. I think mostly people are probably like Beau and I who just kind of shrugged and followed the new norm.  But I thought I would ask the question, now that it’s occurred to me.