In the US, at least in the states I lived in, ISDN telephony was always niche, the price was too high unless you needed it for a remote studio, or you had a tel

In the US, at least in the states I lived in, ISDN telephony was always niche, the price was too high unless you needed it for a remote studio, or you had a teleconference setup or needed the blazing fast 128kbit dial up experience. Analog phones with a digitizer at the central office or remote terminal is still a very good calling experience with minimal latency. 8-bit u-law @ 8000 Hz isn't great audio quality, but the sampling delay is near zero, and when it was all PRI digital (t1/isdn/etc) switching, multiplexing was done per sample, so there was no significant buffering (a two sample buffer would be sufficient at any switching point). Mobile uses complex compression with significant sampling delay and sends data in bursts so there's packetization delay. VoIP often uses complex compression (but you can configure for u-law) and is usually 20ms packets, plus you've got to add a jitter buffer to account for packets taking different amounts of time to traverse the network. Packet switching clearly won over circuit switching, but we've lost the very low latency local calling we used to have, and I don't think anyone is willing to send 1000 packets per second for voice calls to get close to where we were. For long distance calling, probably improved routes that were run for packet switching reduce latency enough to cancel out the increased factors.