A large part of why I don't like Dragonborn and wouldn't include them is my personal heresy:
I don't like dragons. As myths, sure, they work great. And that's the only way they'd appear in a campaign I'd be running, as myths.
Giant uber-intelligent flying lizards that breathe fire/cold/acid/cotton candy/whatever and breed with anything that moves are not something I want to fit into a game world.
Dragon-people therefore really don't fit either.
For the record, I use primarily human/elven/other common sentient race opponents, with some oozes, aberrations and oversized vermin and eventually some fiends. Most of the latter are the fault of wizards creating/summoning things. I'd use a Rust Monster(In fact, there are several my 3.5 party may encounter if they don't start searching for traps in the place they're currently in, placed there by the wizard owner to help take care of any pesky adventurers that come in. He got them from the area of the world that's being corrupted by the Far Plane). I wouldn't use a dragon.
There's also that 3.5 has made me hate running a game and I enjoy mostly the worldbuilding aspect since the players I have are terrible at playing and even worse at actually RPing, so mostly I'm just boredly fudging rolls so they don't die while they mindlessly kill and loot and complain about walking right into the traps they should know by now are there without even trying to look for said traps. So you'd better believe I'm making a world I enjoy, because it's going to be most of my fun.
And I will not use all the races if I don't want them for various reasons - Even ones that do exist may be horrifically rare, to the point of the PC being the only one in the entire world, with what that entails. I'd rather have a few races I can detail than a bunch of races I only throw together some afterthought junk on because they're redundant, or I just plain don't care enough about them to be able to do them justice.
(With the setup I like to use there's also the little issue that anyone playing a dragonborn is going to instantly get cries of 'aaaaaaaaah! monster!' and either utterly shunned or attacked by a frightened mob, since holy crap, giant lizard-looking thing with ginormous teeth just walked into the village.)
Mos Eisley Cantina kitchen sink is nice and all, if that's what you're going for and what you want. But if I want the Mos Eisley Cantina I'll either play a Star Wars game and do it literally, or I'll start a Planescape game and we can have awesomely weird locations to go with our weird monster races.