The association of public insurance providers in Germany provides a limited set of licenses that make psychotherapy reimbursable, everyone else practices in private. These licenses can also be transferred, making them a commodity among therapists.

It's a horribly outdated stance that has pushed waiting lists far beyond the stated legal maximum wait time. This means you can technically get private therapy reimbursed, but the bureaucracy in between (proof you have attempted to get therapy at 3+ places that get reimbursement, filing and often fighting over specific charges) is designed to stall people already fed up with life into simply giving up.

The national healthcare system in Germany to a large extent is based on a command economy.

The number of licenses for psychotherapists - in fact, for any kind of physician - allowed to bill through the national healthcare system is artificially constrained (not unlike the taxi medallion system in New York, for example) by regional authorities for statutory health insurance physicians ("Kassenärztliche Vereinigungen").

This can create artificial scarcity for specific kinds of medical professions, such as psychotherapists in this case.