> This or that restaurant or this or that regional manager could give them a fair wage

They do... usually by way of appropriate schedules or other logistics of the job which delivers access to the richest streams of tips. This is why the good servers follow them.

The conversation around tips and it's appropriateness is largely blind to the other aspects of the hospitality industry. Real people with real jobs responding to real stimulus -- it takes coordination on many axes to deliver a golden hour. The conversation of where on the scale from 0-20% to fall is all bourgeois.