Funny, I thought the same thing about the amount of sick people visiting doctors. The healthiest people I know don't ever see doctors.
* Every day * 5–6 times per week * 3–4 times per week * 1–2 times per week * Less than weekly
Most people I know who go to therapy go once or twice a month. Very few go weekly, and I don't know anyone who goes 3+ times a week.
Also the goal of therapy is to get to a place where you can quit it, so it makes sense that once people are more content with their lives they wouldn't go anymore.
The therapist provides a service with some practice that hopefully leads to some goal, but without excessive professional and emotional investment in the outcome of therapy. After the 50th minute of the session, however, you are on your own.