TinCan owner here. The issue with landlines in my experience is that they quickly become overwhelmed with spam calls. That and the ability to lock down the phone to just a few numbers is the appeal.
Mine, in Spain, is surprisingly free of spam. I receive spam on my mobile phone, which is often blocked by Android, but I don't receive spam on my landline. Strange, isn't it?
There are still VoIP services that function essentially the same. I switched to that recently because the real POTS service had been jacked up in price a crazy amount, probably because we were grandfathered into even having it since the company website didn't even seem to offer it anymore.
Well, I'm sure my landline is not a landline anymore, I'm sure it is some sort of VoIP system, but it doesn't matter, it is a phone with a number, that doesn't leave the living room.