These days POTS lines are usually only used for last mile communications so the calls get converted to VoIP on the telco side. Basically it's for backwards compatibility — the phone lines are already there, a lot of people have phone wiring in their houses and no configuration is required on the consumer's end.

In general the days of having direct electrical connections between two distant telephones are long gone. The telco companies scrapped it when they realized that they could trunk the phone calls from a local branch to the central office using PCM streams over a single cable.