Public phone boxes have virtually disappeared as well, you rarely see someone inside one, let alone a queue to use it. Some of the messaging apps such as WeChat have a facility to call land lines but this isn’t the primary purpose of the app. The number of people wanting to call landlines has obviously diminished to the point where they aren’t making enough money.
I can remember back to the days when mobile phones were becoming widely available to everyone and weren’t a status symbol anymore. People already had a landline in their homes and went out and bought a mobile phone so now they had two lines, which was handy in the days of dial up internet. However when they moved house, there was a growing trend of not installing a landline and just relying on the mobile. Around this time broadband was rapidly expanding and if you had an ADSL connection and a mobile you were all set up.
Wifi calling may be a replacement for Skype. For those not familiar with this feature, basically as long as a wifi signal can be accessed normal phone calls can be made even from abroad without roaming being involved. I have an account with an Australian telco which offers this feature but note that not all mobile phones support it. When overseas with wifi calling enabled, my phone connects to the Australian network through the internet just a if it was in Australia and connecting through the cellular network. Any calls made or received are charged as though I was in the country. It’s also very useful if you have poor network coverage at home but a decent broadband connection.