I don't think that's what he's asking about. I think he's asking why the clones from the old clone army isn't a selectable race. Though if you want my reasoning behind it, clones aren't even a race on their own, just a copy of an existing person.
If it helps, at one point, Stormtroopers were counted as a race, with Carida as homeplanet. They were an NPC-only race. And for much of the beginning of the Empire, all stormtroopers were former clonetroopers.
I don't know for sure why they were removed as such, but my guess is that they were removed because more organizations than just the Galactic Empire had the ability to hire Stormtrooper NPCs, which didn't suit well with aforementioned faction.
That is, of course, just speculation based on own assumptions, so I could be very wrong with that.