Two reasons are Public misperceptions/ myths and money.
I am a counselor trainee, pursuing my Masters at the ripe young age of 54, at Kent State University, seeking to be a Community Counselor. 2 years ago, I had no idea there was a difference between being a counselor and being a therapist.
As several of the posts above mine indicate, there are many people who have no true concept of what is and is not a mental disorder. They assume that if you have a mental disorder, you are "crazy." Family members prefer to live in denial for fear, guilt, other reasons. They don't want people to know their personal business...to know that Aunt Millie has Alcohol Dependence Disorder or Dad has Major Depressive disorder. What will the neighbors think?
But the neighbors would not think that Aunt Millie was a "cripple" if she had torn tendons in her arm or that Dad was unworthy if he had some heart murmur. People could see that arm or notice the slow movements. It is a known situation because it can be seen. Mental disorders cannot be seen, and people have a tendency to make more out of the unknown than they do out of the known.
I read where a Doctor of Chiropractic says there are no tests to help determine a mental disorder, and that is simply not true.
There are several tests-above and beyond mere observation. Some of these tests actually indicate portions of the brain and brain waves that act in particular matters when we experience addictions, depressions, and other disorders. As a counselor, I will not be trained to perform or understand these particular patterns, but a report from a medical doctor would indicate or suggest some of these irregularities.
I have to know Psychopathology, Life Span Development, and be able to make a Diagnosis where one is based on the Diagnostic and Statistic Manual.
Having a mental disorder does not mean one is "crazy," "screwed up" or anything of the like. In fact, as a counselor trainee, I am in a profession that believes in the "wellness model." A psychotherapist believes in the "medical model," that is, they operate from the assumption that there is something wrong, and will perform tests and batteries to help determine what that something is. Assessment is the key to a therapist's work.
A counselor believes that most people are basically well, but have obstacles in their path to healthy emotional development. We do not overlook those who have acute disorders, whether they be acute chemical or other imbalances or other issues. We work with the client to help the client unlock the key, where possible, to his or her disorder...but realize that sometimes that is not possible, and other interventions, a wide assortment of which currently exist,
may have to be implemented.
As I said, another reason for there being difficulty in obtainign help is not just how others feel, but the money. Sadly, because a counselor works from a "wellness" model, many insurance companies do not provide reimbursement. If your family has medical insurance, you might be aware that most of the time, the insurance company will not pay for a regular physical examination, especially as you get older.
Insurance companies (I used to be an exec with one of the world's l;argest) pay to have something that is wrong fixed. Most of them do not pay for preventive care. So, if people are generally assumed to be healthy, unless they report or a family member reports, or some incident happens where they are involuntarily reported, to a mental health care provider for reasons that are covered by the insurance company, the insurance company will not pay.. This leads to fewer people seeking the needed help for their mental disorders. And, yes, it may be costly, although not always, to be treated. Some places do operate on fee paying ability.
Yet another reason is that some discoveries are fairly recent. It wasn't too long ago that Grandma Mary was seen as being some senile old biddie, then they discovered Alzheimer's is an actial medical disease, It has only been the past few years that people have discovered the biological causes of addictions, and that these causes-brain functions--affect not just addictions to substances, but to behaviors, as well. In time, there will be more and more discoveries of the scientific causes of some diseases and disorders. But we are just on the cutting edge of that, The more we understand, the more we can help the public and families that are affected understand.
Until then, the unknown will continue to frighten people.