I do agree that selling stuff / collecting CAN be made more of a "choice", by using stuff like encumbrance to slightly balance it out - the thing is that in most modern RPGs, it isn't.

I really do think there's a difference between the kind of "fun" that comes from collection and fun that comes from solid gameplay involving choices and learning and threats of failure.

Collection is "fun" because it exploits a base human need to gather. In order to help us survive winters and hard times, we evolved a mechanism that releases endorphins from the act of collecting - this is why it's satisfying to collect, while you're doing it. The thing is, it's an empty satisfaction - there's nothing to look back on and be proud of or happy about. Diablo and just about every modern MMO (Especially WoW) basically live, almost entirely, off of this.

Good, solid gameplay - challenges that involves risks of real failure and requires LEARNING to overcome - this is a kind of fun that you can look back on and feel good about. I used to play Diablo, for hours on end, until I noticed this difference. After playing it I would feel like "what the HELL am I doing?!" This is because I'm not learning anything or risking anything in playing it, and even though it's triggering this evolutionary mechanism, after awhile I realize that it's this pointless endless loop. I think that games like that are closer to psychoactive drugs than they are to true games; you'll hear stories of drug users getting the same 'wasted my time' feeling after awhile.

So, in conclusion, it isn't that I'm *necessarily* against collecting specifically, it's that I'm against no-brainers and exploitative game design.