Why do people still have to pay by the minute for telephone calls?

With all of todays technology and automation replacing the telephone operator, that back in the day would have to manually patch calls through to the next party and monitor the calls, why do we still have to pay for telephone calls by the minute?

Factual supported answers will receive highest score. Thank you!

Most of you are missing my point about automation replacing people (operators) that would have to sit in front of a plug board all day manually plugging calls and monitoring them as opposed to todays technology doing it automatically with computers.

Phone companies still have to pay for: electricity, cabling,switches, staff, r&d and last but not least is the Huge CEO salaries. so by the minute is still cheap dial tone

There are many telephone service providers these days advertising charging by the second subject to a minimum charge (usually one complete minute)

That's the plan that they choose.

I pay one rate for everything, with MCI (voice mail, CID, etc. included).

However, my friend is cell only, however she has to have a landline for people to access her apartment and for her alarm system. The cheapest that she could get was a by the minute plan.