On a more serious note, once a company has developed a business model where the cost of acquiring users is less than the lifetime value of those users, then it

On a more serious note, once a company has developed a business model where the cost of acquiring users is less than the lifetime value of those users, then it can make sense to pour in massive amounts of money into getting those users. So I'd venture to say that those companies are in such a position and are scaling UA with the hope to recoup the $$ down the road.