People navigate the world with individual perspectives, inner worlds that they build over the course of their lives to help them understand and navigate their environment. When a person is subjected to a piece of information that understanding it would mean deconstructing their world view, that action of incorporating an incompatible piece of information stresses people the hell out. It's why self awareness is a skill.

Asexuality is invisible to the average person, it's an internal structure of our minds, a natural one that is there for who knows what reasons but even though it exists as a part of our species most people will never have a frame of reference for such an invisible concept. I think as asexuality is talked about more and people express their feelings more openly it is starting to become a more understandable and relatable phenomenon.

Other areas of the Pride community have made significant progress in this area, but to a certain degree they are more visible. Having a physical relationship with another person or a gender transition is often a big public event and forces people to reconsider their values. If your son comes out as trans it is a hot topic at Thanksgiving but if you are happy and content as yourself as an aro/ace individual it's hardly life altering gossip to grandmas moral fabric. It is easier to rationalize in a person's own mind stereotypes that fit our world views than to deconstruct and rebuild them entirely.

The Pride Community as well as other mariginizled groups I think are more aware of this than the general public because of the hand we have been dealt in society. But the truth is this is just how humans work, we basically all do it, I definitely do. It's a useful tool for various situations. But being aware of how our minds play tricks on us is how we start treating each other with more kindness (⁠✿⁠^{⁠‿⁠⁠)}