Especially DMs who have fan forum accounts which allow them to pop into a forum to ask "Hey I've got a player wanting to use splat book X; anything I should look out for?"
That's not a common scenario in my experience.
In the group where I'm a player, we've been playing for over a decade, and only one player ever wanted something "special", beyond the rules the rest of us were following -- PHB from 3.0 and 3.5, and then whatever was pre-loaded in Character Builder for 4e. It might not be a coincidence that the requestor is the only one of the players who prefers 4e, and has gotten deep into the rules of it. The rest of us still use 3e terms and assume 3e rules for things like AOO's . . . in the most recent session, the DM yelled at us for not learning the right rules for 4e.
For my two groups, one has done AD&D, 3.0. and 3.5e. Special (non-core) rules requests have come from 3 players out of more than a dozen that have been in different incarnations of that group since 1996. Two of the special requestors were not looking to use splatbooks at all, but had character ideas that they didn't know how to fit into the rules, and we ended up making custom house rules for each situation because there really wasn't a precise fit out there -- in both cases, it was about getting closer to literary/real world inspirations for PC's, not about min-maxing or reading new crunch. Only one was thinking in build terms, with existing non-core rules.
The other group has had about 6 players and has always been 3.5e core, with no requests for non-core rules at all.
Wanting to color outside the lines of the rules seems like a rare trait with gamers I know. I think that's because we play much, much less often than the alleged weekly norm, so we don't get burned out on normal rules. Plus, if your interest is in action and/or story, creating builds just isn't that interesting or necessary.
Actually, power differences between "buildy" and non-buildy PC's are more noticeable in the 4e game. As I said to another "non-buildy" player, I stick with the feats that give you a +1 under most circumstances, not the crazy stacking stuff where it's +20 if you're fighting a red-headed gnome who's bloodied and you've already cast "breakdancer's mark" on him and are within 3 burst of somebody who's cast "obscure dailies".