Mental illness has long had a massive stigma associated with it. This is slowly getting better as people become more educated about mental illness in general and about some of the more common mental illnesses. Also as
we recognize more widely just how harmful that stigma is, and take steps to address it.
One of the most important things we can do is to speak openly about the topic to reduce the associated stigma and taboos. The more people that speak openly, the more people that will learn that they can speak openly, too. We're not there yet, but we're on the way.
The difficulty with speaking openly is that there are often very real costs associated with doing so. Usually social, sometimes professional. This creates a disincentive to speak openly, but that disincentive and the costs have been dropping over time as more and more people take the leap.