Long before everyone had a phone in their pocket, they were attached to the wall, and the receiver was connected by a cord.
As of 2017, more than half of Americans didn’t even have a landline – they switched to mobile-service only. But for those that still do have a home phone, it’d be a safe bet to assume that most of the actual phones are cordless.
But back in the day, phones used to be attached to receivers by a real cord.