I was a legacy and never really questioned if I would pledge. Also, my college claimed to be over 70% greek among undergrads when I was a freshman. Those numbers have declined in the past 15+ years which is probably indicative of a down swing in fraternity/sorrority membership in general. If I had gone to a bigger school, like UTK, I'm not sure I'd have had nearly the same experience. I probably would've still "gone greek" due to family ties, but I'm not sure how "into it" I would've been.
Addressing the "bought friends" comments, from my own personal experience I must say that I'm very close with many of the guys that were in my pledge class and I still consider them to be among the closest and most trusted friends that I have. Although those guys are spread out all over the South everyone stays in touch and we travel to see one another fairly regularly.
I can also say that any guy who approaches me as a fellow fraternity member (meaning my frat) is going to receive my full attention and sincere consideration, whether said person is seeking a job, advice, trying to sell me something, or whatever. I do not give that same attention and consideration to the average pedestrian unless they demonstrate to me that they merit it. I know a lot of guys in my alumni organization who feel the same way. So, I guess I'm saying that membership does sometimes have its privileges.