Sometimes it's our own self consciousness that causes us to feel that way when nothing is actually happening.

Other times it might just be our body language that we are totally unaware of like a subconscious hesitation here or there hoping they will connect with us even though we might be totally unaware of that behavior & when they don't connect, that subconscious desire makes us feel they are rude when in reality they didn't even notice.

If you have tried to connect before & had issues with people, sometimes people will try to avoid that to avoid getting involved in a possible drama situation.

Honestly without being there & assessing the situation through IRL observation, it's basically impossible for online people to answer your questions.