It’s because psychotherapy is effective.

Campbell, L. F., Norcross, J. C., Vasquez, M. J., & Kaslow, N. J. (2013). Recognition of psychotherapy effectiveness: the APA resolution. Psychotherapy, 50(1), 98.

Seligman, M. E. (1995). The effectiveness of psychotherapy: The Consumer Reports study. American psychologist, 50(12), 965.

Lambert, M. J., Bergin, A. E., & Garfield, S. L. (1994). The effectiveness of psychotherapy. Encyclopedia of psychotherapy, 1, 709-714.

Howard, K. I., Moras, K., Brill, P. L., Martinovich, Z., & Lutz, W. (1996). Evaluation of psychotherapy: Efficacy, effectiveness, and patient progress. American psychologist, 51(10), 1059.

Leichsenring, F., & Rabung, S. (2008). Effectiveness of long-term psychodynamic psychotherapy: A meta-analysis. Jama, 300(13), 1551-1565.