Why is it that most autistic people are excluded and left out?

Back when I was in high school I will try to hang out with peers that are not special but I always get excluded, isolated and left out. Me may of course I had my two best friends which I’m very lucky to still have but I’m not gonna lie to you guys but I was ashamed of a mini that I was in special education. I guess when they found out they either treat me a little bit differently or just stop talking to me. I don’t wanna be the loser and I did not have any friends in high school. I’ve always envy people that were popular had a lot of friends in high school but I did it. My older siblings had more friends than I did in high school. I don’t even know if they still talk to them. My dad preferred if I make friends with people in special education and make friends with autistic people so I can relate. But he said he’s not trying to be prejudice, but it’s better if I can be around people that I can relate to. I mean there’s nothing wrong with that but I want to be friends with people that don’t have disabilities too but I can NEVER CLICK.