Agreed apart from that one line in the middle.
Being nice to someone because you enjoy their company is different to being nice to someone because you want to have sex with them.
Eh. I'm not entirely sure that most guys are quite so calculating or pathological about it. For most, I think it's an ad hoc psychological trap that they just sort of find themselves falling into.
i.e. "I'm shy, kind of insecure, and not great with being forward, so I'm kind of hoping that something develops organically out of getting to know this girl in a more platonic context first, and then I'll make my move when the time feels right."
They just allow themselves to linger there to the point of being self-destructive and unhealthy.
Now, personally, I'm not the sort to rush into relationships myself. I'm cautious. I also meet few enough women I actually click with to I know why one might be inclined to "fixate" a little bit on those that one does (guys who go through women like kleenex usually don't).
I'll go out on a limb here, as such, and say that there's nothing necessarily wrong with any of that, so long as you approach it the right way, and take the hint that she's "just not that into you" when appropriate. Like I said, it's the
other kind of guys, who choose to sit around pining over some girl, basically being her doormat, and growing ever more resentful of her by the day, while she runs around dating other guys, and has long past made it abundantly clear that she's not really interested in them, who've got problems. They just need to move on, and it's their own fault for not doing so.
I've actually kind of got a girl right now I'm probably in the "friend zone" with. I've known her for about a year or so, I kind of like her, and she's made some vague allusions towards being kind of interested in me as well - though she's been dating other guys for most of the time I've known her.
It's different, however, in that I'm not obsessing over her, going out of my way to do favors for her, or tearing down her current relationships. She's just this girl I know, who's pleasant to hang out with, and I wouldn't mind having sex with if push were to ever come to shove (lol). I also know full well that I don't have any reason to resent her over it, as I've never actually made a move.