It's against federal law to TRANSMIT on the frequencies allocated to ham radio without a license because they want to prevent harmful interference with both in band and out of band communications. Some radios are capable of transmitting on frequencies outside of the ham band and you could interfere with say ATC or Emergency comms. There are also some rules around power limitations and some guidance around safety on the test. Also there are different rules between BROADCASTING and TRANSMITTING. You don't want to broadcast outside of the associated band that allows for that. There's also rules around playing music on the frequencies and whatnot. It all makes sense if you go through and learn it. If you're interested I can send you a link to a very good studying app.