True, and one doesn't need a driver's license to know how to drive -- but a system of licensing is the most efficient way of verifying qualifications.
What difference is there objectively between 'a certified software engineer' and 'a programmer' ?
Licensing helps, but it can be abused. Unlicensed anything isn't necessarily a bad thing, and, legal and mental affairs notwithstanding, buyers should be able to choose between multiple options.