It's just a matter of editing standards, such as those broadcast adult channels have to adhere to when broadcasting to certain parts of the USA - some states can only be broadcast XX (no cumshot or anal), while others can have XXX (cumshot and anal), while even others can have XXXNA (cumshot but no anal), and the list goes on and on.
For the web, there are plenty of people who don't want to see the cumshot, mainly, I'd guess, because it's usually extended footage of some dude's funny face as he jerks off onto the chick, or those couples who are just not into the hardcore XXX stuff.
