For others it's a way to build status back in the home country by having attended a US university, and then go back.
For others it's just a way to hang out in the country, while paying someone else to do all of the exam-taking for them. The wealthy Chinese-dense "626 area" in SoCal comes to mind as one of the big offenders in this underworld. They don't even show up to class, someone else does. There's no incentive for universities to police this, why bite the hand that feeds? The school gets a few hundred k in revenue, the wealthy student gets to live in the US for a few years, have fun. It's a win win, even though it corrupts the point of an F1 visa. Unlike H-1Bs, I don't think they're limited, so at least it's not a zero-sum game where some other "more deserving" students are screwed out of a place.
Just like decoupling health care from employment is a good idea, decoupling for-profit education from immigration seems like a good call as well. Unless we're on board with immigration being pay-to-play, vs using other markers besides family net worth in order to gate keep.