It was probably 1983 or so when New York Telephone (now Verizon) upgraded our exchange from electromechanical switching to an AT&T 5ESS.  I clearly remember the day when I finished dialing a friend's number and didn't hear that satisfying "ka-CHUNK" indicating that you had successfully dropped a trunk line and the call was on its way.  I also remember shortly after that, using touch-tone on our line even though "we didn't have that service."

Adding touch-tone to a line served by mechanical switch required modifications that really did cost telco money.  On an electronic switch it was just an intrinsic part of the system, but for several years they tried to get away with continuing to charge extra for it.  I used tone dial on my modem and when telco tried to slap us with the fee we told them, "nope, not paying for it, shut the service off."  I knew they didn't have the ability to do that, so they simply took the fee off the bill.

That was a generation ago, when my dad was skeptical that I could even make a touch tone dialer work, and even more skeptical when he brought in the phone bill and I told him we can easily refuse to pay for tone service.  Today, my kids wouldn't know how to use a rotary phone if they saw one (Wes would probably figure it out, he's into that kind of stuff) but it's fun to think about how the dialing isn't even decoded by a switch at the telco, but rather by a 612A ONT in the basement that terminates the analog leg and sends the call out digitally over fiber optic cable between my home and the central office.   And long distance is billed at a flat monthly rate -- who'd have ever thought?