You don't have to be a certain age to have used modems. You used one today to send that comment! Likely more than one. Radio, cable, and fiber don't carry bits

You don't have to be a certain age to have used modems. You used one today to send that comment! Likely more than one. Radio, cable, and fiber don't carry bits. They carry waves - analog signals - just like an old fashioned copper phone line. They all need a modulator-demodulator to convert between bits and waves.