- PSTN is well-established. The phone network has had global reach for a very long time, probably longer than the Internet. Phone numbers have been part of pe

- PSTN is well-established. The phone network has had global reach for a very long time, probably longer than the Internet. Phone numbers have been part of people's lives for a century. - Some locations in some countries are probably still using mostly analog switching equipment and can't upgrade to cellular or anything more modern/secure for various reasons. - PSTN has government-agency or at least a subsidized/privileged monopoly status in most countries, so it won't die a natural death. I just wonder why it took until iOS 12 or whatever for my phone to be able to drop calls from unknown contacts.