Because all the other species in the game aren't Human.
They are not human--but they are sapient beings with self-determination and personal identity. Why is it their sapience, self-determination, and personal identity are
always trumped by their physiology?
That's the point: the game was originally designed along the lines that Humans are supposed to be the species that can do a bit of everything, while the others are better than us at some things and worse than us at others. I've never seen any good reason to change that foundation, even after in effect kitbashing and rewriting almost the entirety of 1e over the years.
Completely missing the point. I'm not saying every race should be "can do a bit of everything." I'm saying that every race that is capable of being a player character should have sapience, self-determination, and personal identity. Sapience being human-like awareness and intelligence: the ability to understand oneself as distinct from one's environment, to reason about the world around oneself, etc. Every playable species should have this trait in order to be, y'know, playable. Self-determination should, I hope, be self-evident, but just in case, it means the ability to make one's own choices for how one will live, what actions one will take, etc. (Obviously, some situations like dictatorial regimes or slavery or the like can severely degrade a person's ability to
exercise their self-determination, but they
have said determination nonetheless.) And, finally, a personal identity is individuation: all the personality quirks, verbal tics, tastes, preferences, dislikes, turns of phrase, etc. which make a person distinct from other people.
Hence why I agreed with the notion above, that a truly eusocial species, one with a "hive mind" or autonomous but not independently-thinking drones or the like, would be one of the few ways to dodge the above--because such entities would lack at least two and possibly all three of the above qualities (they might or might not be sapient, but they certainly wouldn't have self-determination nor personal identity.)
If Dwarves possess sapience, self-determination, and personal identities, why is it their
species is what makes them special? Doesn't that erase their individuality
worse than the other way around?
Er...yes it is: saying something can't happen heads off any problems - balance or otherwise - it might cause before they even have a chance to manifest. And through 40-odd years of trial and error I've gained a little bit of wisdom when it comes to seeing problems on the horizon and stopping them before they get much closer.
Again: no it's not. Because you had to patch something in
at the end, after everything was said and done, because the combination of those things would be broken. You had to
ban something. That's--by definition--
after the problem ("A wizard with too much health would be broken") has already happened. A Dwarf Wizard
would be broken, therefore you are now
forced to ban them. Cutting the problem off at the pass would be asking either, "How can we make Dwarves still be really robust--important for them in several other classes--without making Dwarf Wizards overpowered?" Or, though I don't think this would be as effective, "How can we make the Wizard generally balanced around physical frailty when some races bring strong (even, potentially, extreme) natural robustness that could completely eclipse that?"
As an example of the latter, consider the 13A Necromancer. One of its class features actually
punishes you for having a positive Con modifier (and, if you invest feats into it later on, you can actually get
bonuses for having a negative Con mod.) Something like that is a brilliant design move, because it doesn't
force players to never play Dwarf Necromancers (for any reason, balance or otherwise), and instead gives them a reason why they
shouldn't choose to do that. (or, well, it would in your game's model of stats. 13A stats work differently.)
Yes, and banning something up front is that ounce of prevention.
Er...no it's not. It's a pound of cure. Prevention would be the situation where you don't need to ban anything in the first place. Dropping the banhammer IS the prevention!