I agree. Besides for the occasional comments regarding your race, there isn't much different from choosing to play as a dark elf or khajit in the elder scrolls. I imagine if they did make choosable races, it may end up how Yamu described it, a few slight adjustments to your starting SPECIAL stats, and perhaps a perk or two..other then that it would probably be more for looks.
But imagine choosing to be a super mutant and the beginning for that would be getting pulled from a vat of fev, maybe different places wouldn't accept you because of this, maybe you even have a whole new story line available to you because of this. Then the obvious things like lower intelligence, increased big guns and melee, maybe a low speech skill.
Ghoul would receive a lot of discrimination from humans but you could interact with different ghoul groups that maybe you wouldn't be able to otherwise. Maybe make available a new route for the main quest for them as well. They would have benefits such as being healed by radiation instead of being harmfully affected by it.