I'm not old enough to remember firsthand, but I believe rotary phones (in the US) are generally from the era when the phone company was a monopoly and strictly controlled what was plugged into their lines. So I think it may be technically correct to call them a (part of a) utility and not just an interface.
Yes. The telephone in your house belonged to AT&T, and you had to rent it from them. It took a lawsuit for them to allow other devices to connect to the phone network. Today's vendor lock-in is no different.
I'm not old enough to remember firsthand, but I believe rotary phones (in the US) are generally from the era when the phone company was a monopoly and strictly controlled what was plugged into their lines. So I think it may be technically correct to call them a (part of a) utility and not just an interface.