Well, there’s HAVING a radio, and USING a radio.
I’m based out of a uncontrolled airport nested within easy range of three controlled fields. Instructors often bring their students here because they can pack in more landings.
And, in some cases, they turn down the radios because they find all the calls “distracting” for their students.
I was president of the airport advisory council, and we sent a polite letter to one of the FBOs requesting they stop the practice. They responded with a refusal, saying use of radios wasn’t mandatory.