On dialing they might be cosmetic, but the tones are still used to communicate with remote services. When the machine says "Press 1 for English," it's relying on getting the right tones (1209 Hz and 697 Hz in DTMF). Sure, they could be sent in the background without letting the consumer hear them, but they're still being generated.
Except few modern devices actually transmit there frequencies in-band. They get encoded and sent out-of-band, then recreated (if needed) on the other end.
http://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signa...