Exactly. in order to grow, they'll need investment capital. Those investors will want a return on their investment and, they'll insist on a site that's capable of being monetized. Creepshots, vitriolic, racist hate speech, underage pics and, shaming fat people just are not anything that's good for a business in the long run.
Likewise, it doesn't occur to the users that they might be the problem. That's why Reddit is filled with ex Diggsters and 4Chan rejects. Good luck not having the exact same problem in 5 - 6 years at Voat.