Why do people think autistic people are only supposed to date, other autistic people?

Both of the answers here so far are total BS. I have mild Autism, and I am certainly not "mind blind" as one of the people here claims all Autistic adults are. What a BS statement. I also don't LACK empathy for other people. That's also BS. On the contrary, if I have a flaw, it's that I feel TOO MUCH empathy for what other people suffer. I've also been accused of being too trusting. What angers me about the way adults with Autism are treated is the belief that we are supposed to all be mean or incapable of having any positive feelings about anyone. That's nonsense. I experience the same emotions that anyone without Autism does, but I do experience them differently. And if I wanted to date, I would date whoever was interesting, Autistic or not.

Not everybody thinks that but I can definitely see why that's a common perception.  You know what they say, "once you've met one person with autism you've met one person with autism," and yet relationship threads where NT partners of ASD people report very similar frustrations and conflicts that just don't appear in the "usual" kinds of relationship problems that relationship boards deal with.  These threads are habitually gate-crashed by asd people who deny that these issues are real and the way they express themselves is so similar that you could be forgiven for thinking, "once you've met one person with asd you've met every person with asd."  The relationship challenges are real and very specific to the asd - nt dynamic in intimate relationships.   Not everyone will have problems, but if they do they will be very specific ones and not everyone is cut out to cope with them.  The unintentional emotional harm that someone with mind blindness and empathy gaps is capable of doing is enormous and they won't even notice that they're doing it.  Some NTs never recover and never go on to have another relationship again because they're so badly burned.