They're there so the owner of the club/restaurant can relax, not you.
Right now, I feel like this guy is useless and I don't want to give him money and I feel bad about that, like by not paying him I'm calling him useless.
If it were for the owner, and that was clear, I'd feel great because I was making his job easier by not causing any trouble or mess, and on top of that, hey thanks for the towel!
But it is one of those weird things that survives long past the point of sense, they should just be paid a wage and be employed rather than work on this weird charity-basis. It's a bit akin to waiters in the US working on tips, whereas the rest of the world just pays them a normal wage. The clubs bank on guys with 10 beers in em to both be drunk enough and close to bursting enough to pay for the service.
The highlight of that experience was the drunk lady who stole a toilet lid in the men’s room.
Japan can be even worse. I’ve seen it at hotel seven when you’re eating at the hotel restaurant.
The toilets at St Pancras are free and always have been. He was just some random guy you gave money to!