Because they can or think they can get away with it
Some whores just blatantly take the piss
Why this bothered me so much is he willingly tipped her I visit this brothel quite regular, even though I have no interest in seeing this girl I think it's a very slippery slope to start tipping prossies because you feel she gave you a remarkable service.
some punters are complete mugs
It's a deadly combination for them and for us (at least those of 'us' who have a modicum of common sense!)
It tends to ruin the game for other punters. Like Americans who come over and tip bloody everyone (years ago you used to be able to go and enjoy a decent strip show,much hornier than the ones now, simply by paying an entrance fee, not with grovelling additions each time a cow lifted its garter leg). It creates an expectation. Eventually it creates a dual pricing structure, ruinous to normal people. (on a bigger scale the United Nations did it in Cambodia, until ordinary people could hardy afford to eat, market forces adjusting themselves to what UN salaried people could and would pay).
There is another name for such stupid punters – traitors. Another inch and it is often the same induviduals worshiping the pro$$ies arse, writing love-letter sick reviews, warning her about any comments on UKP and promising her servile lifelong devotion.
And does it do her any good? That is very questionable. It is like giving money to a professional beggar. Instead of encouraging them to be able to support themselves with honest work it rewards non-work, creates dependence, makes the main aim to get money for nothing rather than earn an honest fee, even as a prostitute. It can turn a marginally decent whore into a complete cunt (of the bitter, conniving nazifem variety, not the divine vagina that bringeth the joys of her union to mankind).
Punters that do shit like that are not kind: just stupid.