Not to avoid letting down customers, but to give herself an accessible aura, if she's fucking a roommate she may even fuck you! It's like when girls tell you they love blowjobs or anal just to impress you, well at least girls of my generation used to. If she says she's in a committed relationship and doing this for some money on the side it won't get the dopamine and credit cards going the same way now would it?
What I can't fathom is how that guy can't muster the effort to put on a show, it reflects on his manhood. Surely he's seen porn before. He's roided up, so pop that viagra and a speed/meth hit and off you go lol. Just low IQ low effort all-around.