why dont people understand autism?

I had a project team member for an AI class once. He was diagnosed with autism and relied on some medicine to keep himself a little more balanced. All in all, he was nice I think. While you were in his circle, he tried (to the best of his abilities). If you were outside of that though (like if he wasn't involved with you) you didn't really register to him. His anxiety constantly led him to dominate discussions and lectures with questions and requests for clarifications to satiate his uncertainty. Even to me it was trying, as it undermined the team's needed cohesive front. But I would blame that on the lack of awareness of social cues and minutiae. Overall, he was a pretty smart guy that would be even more so if he wasn't held back by his need for reassurance and seemed like a decent friend to have, since he likes games and anime haha. I would need to weight my capacity for patience and communication, if I wanted to work with him on another software project though. He oddly mistook one of my deadline clarifications as making fun of him. Not really sure what to make of that one, I was confused at the time