Because Asburgers Syndrome makes finding anyone, aspie or not, difficult? Most aspies do not have the largest and most diverse of social networks.
But really, studies show when two aspies reproduce, you get a ridiculous chance of full blown autism, probably some co-recessive type thing. This I can attest to anecdotally from my family. Better find a woman who doesn't quite understand you but doesn't have that gene, your offspring will have at most Asburgers Syndrome.