If power or internet goes out, wired VOIP phones won't work. Both the power and the internet have way worse reliability than the copper wire telephone where I live in a top 1% part of California.
If cell phone service goes out (or if cell phone batteries get exhausted and can't be recharged), then mobile phones won't work.
A landline is a very, very reasonable "emergency line" or even "regular line". The data and power connection to it will not be unexpectedly severed, for the most part.
I can very easily imagine an "extended outage" for whatever reason of power, internet, and/or mobile phone service, take your pick. In any of these cases, I would expect to basically be able to use the landline phone to call a relative, friend or co-worker pretty much anywhere in the world. Ok, maybe some disasters take out copper wire telephones, or maybe sometimes copper wire telephones have issues (rare but possible), but this is still a pretty good backup/emergency/constant connection.
If you really have got your sh* together, you have a landline, IMO.
There is a copper contact running all the way to some box, and to some substation, which has utility-managed diesel backup generators and switching and all that jazz. I don't care if it's digital and so forth behind the scenes. It's managed! It works from their system to mine, end of story.
We have a residential elevator. It has a phone line for emergencies, like if you get stuck in the elevator by yourself. That goes to a copper wire telephone wire. I do NOT want to rely on the unreliable California power utility to not have a scheduled or unscheduled outage, causing the elevator fail, and also shutting off power to a cable box powering some VOIP service. Really?
Sure, I could add backup batteries. Sure, I could add automatic diesel power generators. But, the phone company already has those! Do I need a secondary and/or tertiary ISP as backup as well, and somehow join them together? (Some will say, "yes, of course".)
What are they going to do next, ban standard incandescent light bulbs? Oh, wait, they already did that! Alexander Graham Bell and Thomas Edison must be spinning in their graves!
I get the idea is to cut costs or something, but I think this is a safety issue, no?
If we can't have real light bulbs, and we can't have real telephones lines, is there a name for that? We used to have more or less "additive" technologies. A new one would go add to the list of available technologies, not really fully replacing any. Just adding to the list of what you can readily have/do. But this concept of "removing" solid technologies for arguably "worse" ones--I think it's not merely enshittification. This seems like a whole 'nother branch of weird.
Maybe there's some state that will reverse some of this stuff; one can hope, can't one?
If you use one or more copper lines: what is your plan for the post-telephone-line world, if it comes to it?