exactly, I guess the porn world is not just for some girl doing just whatever they want, it's supposed to be a job, is not their private lives and is a pornstar is requested to do something that fans would like, maybe she will do it, maybe not, but suggestions are valid.
I'm the kind of man that want to see girls doing interesting and new stuff with the passing of time, I think Rachel have been doing the same old thing for at least 2 years, just the same way, the same theme, the same positions, and the same cum taken in face or tits. It let me see that maybe she is just working, not committed to the moment, just doing it to gain some money and entertain some people. Some times in her last videos she doesn't even scream like she did before, there is a passion included too that plays an important role turning men on and desire to fuck a woman like horses.
I agree it's not strictly needed that a woman to go black to improve her porn work, it's just a suggestions that many guys like to watch it, a girl being penetrated deeply by a guy like an animal, but there are some other things that works too, the important thing is to DO IT!