I would expect to pay for the tip, but don’t think I would be bothered if people offered to contribute towards the tip.
Me and The Wife went out for a meal with friends once, and the service was shocking. Glasses were dirty, and my meal turned up 10 minutes after everyone elses, was all dried out and the sauce has a thick skin on it. I suspect it was left on the serving whatsit. The waiter was miserable when I asked where my food was.
Our friend was paying and asked us to contribute to the tip, he was annoyed when i said “I’m not paying a tip, the service was shite and my food was horrible”.
Everyone elses food was pretty crap too.
Apparently that friend now thinks I’m tight…*shrug*…I’m not the one who offered to take us out for dinner and took us to The Harvester. We paid the last time and took him to an expensive gastro pub.
Never did like him anyway.