It's more that 3.X is designed as a miniatures game. So many rules and feats and skills (and therefore PrC's) require the mat.
I like the basic mat free game style. But you can't really play that in 3.X and use the 3.X rules effectively. The game assumes you're using a mat/grid/etc. And if you play without it the game system doesn't mesh with all the rules. Like in my comment above... I played with a (3rd level) character who had +3 mod to dex and combat reflexes in a recent mat free game... Other characters (I was the newbie in this group) picked things like rapid shot/flurry/two weapon fighting. We got into a mass melee, basically a low level army with opponents everywhere. I only got one attack per round, they all got two. But I had the 'potential' for four attacks per round. In a melee with everyone moving around/etc (as was described) I definitely should have gotten more.
Was this the GM's fault or the playstyle's fault? In part... I don't think anyone in his games had ever taken combat reflexes (why should they? It's useless!) I don't think he looked at it. I'm sure he would have done something to take it into account if I'd brought it up, but I didn't know how. In fact, there were a couple of battles that my character sat out completely and just watched, because he wasn't sure what was happening, or that he was supposed to be involved... I imagine if I keep playing with them I'll bring up the CR issue (I took it because it's a prerequisite of a PrC I wanted in), and I'm sure there will be a reasonable ruling.
But without a battlemap what could that ruling be? A simple +1 attack per round? I've got +3 to dex so that's quite concevable as an average... But wouldn't they sometimes use tactics to get around that? But wouldn't I use countertactics? On a map, yes. Completely in the air? Impossible to really determine. I can't see really taking that feat in that style of game.
And that's just one example. I'm positive there are many others (I can already think of more than it's worth the effort to type in)