He's getting his money's worth out of that fat white ass. I love the (usually black) guy fucks fat cheap hoe in car or in dirty house genre of amateur porn. These women are usually married and are sent home with a nut in their fat ass. And I suspect both the husband and the john are happy pimps.
I don't know, there are certain big dicked white guys that can't get enough of these fat older white women with large asses and watch a lot of this type of porn. I suspect these women are too loose to say no to any of them.