I don't (and never intend to) play for money, but we notice the same thing when we go to the pub session at Audlem.
There's a really nice crowd go, quite a diverse mixture of singers and tuners, tolerant of each other. And there is a board outside saying 'live music Monday'.
The atmosphere varies according to the 'crowd' standing at the bar. The musicians fill most of the seats.
Sometimes we have the place to ourselves and we can play the slow stuff, experiment a bit, listen to each other. As well as the all-join-in chestnuts.
Last night the bar was crowded with people who spent half the time shouting at each other, the other half joining in lustily with the choruses (Wild Rover, Whiskey in the Jar, in a key we could all play along to), laughing at Ian's comic songs (he has a loud enough voice to sing unaccompanied and command attention in any setting), and jigging around to the tunes. It was a night for playing things that everyone knew and would join in with, raising the roof a bit.

Either way we can enjoy the evening.

But if you are paid it can be diconcerting to be booked for something which doesn't work - at least as a caller if people won't dance I can turn roud and ask the band to give them a tune.