If I knew the sexual orientation of my waitress, I would be far less likely to tip. When I eat out, which is not common, I am not there to hear about a stranger’s bedroom activities.
I’ve had dining partners comment to me that the server seemed to be weird. But even looking weird isn’t an infallible rule today; some straights ape gay looks just because they think it’s cool. A guy with a bodacious earring once waited a table where I dined and I thought for sure, gay... till I overheard him talking about his ex.
Snap judgments have a way of coming unfastened.