There are other reasons as well.
I'm well aware that the providers I meet with all likelihood don't find me particularly physically attractive. I'm 36 and a bit inside the "overweight" BMI category, and - as such - not very attractive to young guys from 18 to their early twenties (who are the guys I'm looking for). Thus, I have to pay to meet them.
So I'm not naïve and I don't make any illusions that the young guys find me particularly attractive - otherwise I wouldn't have had to seek out guys specifically looking for money in exchange for sex (I could meet quite a lot of older guys for free if I wanted to, but sadly for my economy, I don't).
Nevertheless, that doesn't mean I'm indifferent to the young provider ejaculating. On the contrary, it's very much a turn on for me. Both because I find a young guy's cum quite tasty - and because I like the submissive nature of the act of getting cum on my face or in my mouth.