The more generous might interpret this as 'networking'. The less generous might interpret this as 'pseudo-nepotism, mutual backscratching, and insufficient reliance on one's actual skill'.

Since when was the latter not a definition of the former?

As a more serious answer, I had an actually-Greek roommate who ended up in a fraternity and his commentary was that a lot of them hold semi-regular meetings with alumni and try to establish an external image of professionalism (Dress well, cultivate social / sociopathic behavior, "look rich"). Meanwhile alumni who've been on the inside turn a blind eye to the many hours of partying and toss out favors when they know their company needs interns. If you're an idiot, it's expected that the system will weed you out eventually, but to the rest, it's a foot in the door.

Compare that to the alumni from the frisbee / public service / poetry clubs, whose aid to younger members is basically non-existent and you can sort of see why it exists, even (Especially!) if it's just a massive game of buddy-buddy.