The majority of people do not have the interest or care to acquire a sufficient comprehension of psychological disorders and illnesses. Mental health issues are not visible, which causes uneducated people to brush them off.

Like some posters have already stated above, people will only go out of their way to research mental health if;

1.) They have a genuine interest in psychology and mental health. 2.) They suffer from a mental illness or disorder themselves.
3.) Someone they know or someone who is close to them is suffering.

And even then, you can't expect people, by their own volition, to take the time to try to understand. Even if the resources for gaining knowledge about certain subjects are at their disposal, people won't go out of their way. It's laziness and indifference on their end.

Unfortunately, there isn't much you can do about the media being a contributor to the stigmatization of mental illness and prejudice against mentally ill people. Another contributing factor, of course, is the label mental illness, it's associated with extremes like psychopathy and psychosis by the average person, resulting in fear and misunderstanding.