Partly yeah, radio spectrum is a limited resource. All users of radio spectrum have to work within agreed-upon limitations. Further, radios can be dangerous. Someone operating radio transmission equipment could harm others or themselves if the equipment is not being used properly. There are many regulations around the usage of radios and "proving" one is sufficiently aware of these regulations is also part of the reason behind requiring a license. In Canada we don't call it a license, it's merely a certificate of proficiency, to indicate your capabilities/knowledge in respect to the amateur radio regulations.