People don't realize, you couldn't just buy a phone - you had to use the one provided by your monopoly phone company. It was only after breakup that there could

People don't realize, you couldn't just buy a phone - you had to use the one provided by your monopoly phone company. It was only after breakup that there could exist an ecosystem of phone peripherals like answerphones, direct-attach modems (this is why acoustic couplers were a thing), cordless phones, etc.