Incenjucar
Legend
A race, as a whole, is balanced, ideally. Individual racial options are not all equal. There would be a risk of something like combining the tiefling and dragonborn +1 to hit bonuses (thankfully they at least won't stack), or combining them with a human, elf, or deva, for extra-absurd to-hit bonuses once per encounter. It's basically scattering eggshells for designers to walk on. And, again, it prevents them from creating UNIQUE hybrids like half-elves and muls.