I can only speak from my own experience but what I've found out is relationship requires expectation and commitment, that creates pressure and can raise anxiety. Aspies aren't very good with coping with that, not to say there aren't some who are. Then there are sensory issues with being touched and such, I suppose there isn't much you can do with somebody who isn't willing to be held. For me, it's difficult to even hold hands and what my partner wanted required a lot of touching, not going into detail but it should be obvious what I mean. Sure there are ways to work around something like that with patience and understanding but with the combined strain of it being so hard to express oneself, it can feel helpless. Not to say it's completely impossible because I do believe anybody can find love if they really try. For me, I was dating another aspie and we both kept making so many mistakes and had a failed communication and at this point, no matter how in love we fall, it seems futile.