A lot of it is denial as well. In the mental health realm, for example, I meet a lot of Boomers who show obvious signs of ADHD and/or Autism and they haven't the slightest idea they have it.
If you ask one of them to get tested, they'll just stubbornly refuse and insist there's nothing different about them, even when you point out their symptoms to them. "A lot of people do this; doesn't mean anything!" Yeah well a lot of people are neurodivergent. Something like 30% of the population has ADHD, for example.
Just because a lot of people have a mental health disorder, that doesn't give you an excuse to just ignore it! You still need treatment and therapy.