I get where you're coming from, but you're basing your conclusion on too small a sample; people you know or have heard of.
To my knowledge there has never been a comprehensive sociological study of people on the spectrum and their ability to form relationships with NT people.
I am a self diagnosed Aspie - going for formal diagnosis on Friday, and I have dated a number of women, only one of which I suspect was on the spectrum, and only one of whom has a diagnosed disability, the rest would have been NTs.
I will grant that my relationships have been difficult, and that I divorced my first wife who was an NT, but this was about incompatibility, a series of stressful events that broke down the relationship, and a conflict between her need to feel in control and my need for a sense of stability.
So in summation; Aspies and Auties can and do date NTs, it's just that relationships are difficult, and for some the struggle is too much for them to feel it is worthwhile making the effort.
Also, as ASD seems to have a genetic component, dating across the spectrum must have been happening all along, otherwise either NTs and ASD would have either started to evolve into different non compatible species, or ASD would have been wiped out due to reaching a genetic dead end.
Similar to the now disproved theory that Neanderthals did not interact with or breed with modern humans; DNA research has proven that we all have a bit of "caveman" inside us.
That said, I would say very severe ASD cases would often not date, as they have difficulty with communication and interaction in general, and often lack the independence to "launch". You can't date if you can't communicate.