Lack of hybrids in the basegame.

Ive been playing rimworld with biotech for a while now and i dont really bother managing the relationships between colonists, I let the game sort itsself out. But i noticed that every so often i get a hybrid baby. Which makes sense in the mess of random colonists i tend to recruit.

But ive never in my life seen a random hybrid pawn in any of the other factions. Even tho many factions have multiple different races living with eachother. So how come there are never any hybrids in raids, caravans, or other events?