That's kinda my point though... You could do these challenges without having the achievement system in place, just find a challenge and do it. I mean, back in the NES days you had people doing White Mage-only runs of FF1 as a challenge, without anyone telling them to... For example 
True...
I think though, that some gamers (myself included) are just...
"Completionists".
When I platinum/100% a game - it's for my *own* satisfaction.
Sure, part of my 'completionistic'-tendencies likely stem from me (sometimes) feeling like I'm trying too hard to...*prove*...something (to myself, though).
Ex. Cross Edge, the game I just (re)platinumed.
I bought it because I'm a big fan of RPG's, the PS3 had a sorry-ass amount of options for RPG/JRPG fans, and because I'm a fan of (and had already played) many of the games that the cross-over characters originated from; so I was looking forward to the jokes, easter eggs, references to those older games, etc.
That's why I *bought* & *played* Cross Edge.
The reason (at least the *MAIN* reason) that I commited to & dedicated myself to actually...
...
*"Platting"* / "100%-ing"...
the game, though, was because I'd heard *A LOT* of players talking/whining/crying about how
*Hard* of a game it was to platinum.
Since I not only have
"issues" (more like, I have a
*Subscription*), I quickly get to thinking "Hmm...such a very hard game w/ so very few gamers who actually 100% it" (compared to the majority of other games that have much more people 100%-ing them), "well now, if *I* can 100% it (one-handed) - I'll feel like I've actually accomplished something that most "normal" (2-handed) gamers have struggled with".
I know, I know, it's probably kind of a fucked-up kind of thinking, but, I'm a pretty fucked-up kind of person - so we get along w/ each other pretty well
Anywho...back to what I originally came here to say...I'm not one of those people who (everywhere possible) links a bunch of strangers on-line to my PSN account/Trophy cards, etc. (nothing against those that do, though).
The only people who will really ever even know about/see what trophies that I do/don't have will be my "PSN friends"...who fortunately, like myself, don't much care about/compete w/ those kinds of things.
Personally, I've been a "completionist", 100%-ed games, and did (my own challenges/playthroughs) since long before there were any kinds of trophies/achievments and/or recognition for doing so, so, I see no reason to stop (or not enjoy) doing the same kinds of things now
