I agree and we shouldn't be encouraging the expectation of tipping. Next thing you know we'll only get decent service when you tip.
On the very rare occasion that I tipped it was because it was an extraordinary session - very extraordinary. eg. She nearly doubled the 1hr time with full service the whole time and 4 SOG plus windown afterward which took the session over 2 hrs and 15 minutes.
Yep, 4 SOG in 1hr and 45 minutes - 2 BBBJCIMSW, 1 regular SOG and 1 BBBJ/CIM/COF - that was in my much younger years - today rare to get off 2SOG.
Anyway, so unless you are in an extraordinary situation - don't tip is my recommendation.