Interest to friend: is it possible?

Yesterday, the topic of being just friends with someone you were never just friends with came up in conversation. Because I'm optimistic about any situation, I had not questioned just being friends with THE as a possibility, or anyone else for that matter.
              Bestest, however, pointed out that some guys do not want to hang out simply as friends, but would rather continue to hook up, or whatever it may be that you were doing before. I guess some guys will always fall into a different category. Friend, crush, hook up* only, or more. Within each of these categories, I find there to be sub-categories.
               For example, I have friends who I'll always have a crush on, but I could never date because they're not right for me. Or I have friends who definitely have crushes on me, but I'm not attracted to them. Or, the worst kind, a great friend, who I want to date, but he doesn't want to date, right now...
               Now what about those people who always want to hook up, but that's it? Then what? Honestly, I think that you can go from hook up to friend. I've done it in the past, but will it work this time?


*Hook up -- a controversial term because there is not universal or agreed definition; for me, I use it in the sense that one is engaging in sexual activity, but not necessarily sexual intercourse