Disadvantages I have faced dating wise by being on the spectrum:
Inability to tell if a girl is interested due to not being able to pick up on the non verbal cues
General awkwardness makes a poor social impression, often killing attraction that would otherwise be there
Isolation and being on the wrong end of bullying kill confidence. Confidence is often seen as sexy, so this also kills attraction
Differing body language gives off different signals (you may act differently to show interest than most people, and most others will often not be able to tell your interests)
Unsure of being able 'how' to ask someone out often means you can't make the first move, which society expects the male to do
Naivety of sex at a young age comes of as unattractive and unsexy
Lack of experience exaggerates many of these traits at a later age