Its not a medical insurance as such. The charges are to fund the regulatory body.
This protects the professional title and offers reassurance to the public that the individual professional has undertaken the standard training and been adjudged fit to practice,(passed the exams) that they have kept up their professional development and that they are a fit and proper person to practice which covers things like deliberate or accidental malpractice, personal behaviour (drugs, alcohol, honesty, ethics and so on)
Sadly we are becoming a more litigious society and this is is one of the consequences.