I pay to get them to do what I want and not to do what I don't want.
Once I cum, I'm normally finished.....when it's a free hookup, you feel obligated to help get the other guy off and I've been on the other side of that coin with free, they finish and say they are done , leaving me hanging, karma.
I also don't like to suck dick much anymore or kiss (never did, too gay) and when a MB says suck my dick, I laugh and say 'Hey, you're the one being paid, suck mine"
SO paying, allows me to set the rules, so to speak and set the scene..... I'm always upfront with what my likes/dislikes are and what I'm expecting before closing the deal.... also making it clear that if they can't perform (stay hard) or cum, not to expect the money we've agreed on, so there's no surprises for them..... a couple took it as a challenge and really performed. One guy when going with me, said he will give me 1 hour...I said one hour? We finished in 30 minutes, so I reminded him he said one hour as he was getting dressed, his eyes widened realizing he shouldn't have said anything, that sword cuts both ways.... I had him give me a massage for the remaining 30 minutes 😉