Is VOIP included in "landline"? Or is "landline" only "POTS" (Plain Old Telephone Service" - copper wires to your home with 48 V and analog signal)?
Either way, as some have mentioned there are plenty of reasons to keep a "landline" phone, regardless of age.
We have a base with multiple wireless extensions. This means I can pick up a phone from anywhere in the house, even the basement or garage. Those extensions sit in chargers, so they are always at 100% charged.
That alone is a big advantage, compared with coming home, putting your mobile in a charger, and then needing to run to it if it rings. Why would I want to do that?
And what about being on hold for 45 minutes, after being transferred 6 times and finally getting someone who can help you? Unless your phone had a good charge before the call, you risk getting dropped, or having to have the thing plugged in while talking, which is awkward. With a "landline", I can walk over to another extension, pick it up, and use it, and the place the other extension back in its charger. And those batteries last a loooooong time, so even that would be rare to need to make a switch.
Plus, there are advantages to the old fashioned "answering machine".
Now, the age issue - some of this is from having a landline for so long. People know that number will get hold of either of us. It's convenient in a way. Some of that is inertia, but that's OK. 'Kids" who never had a landline may just not know what they are missing!
Plus, we use very few minutes on our mobiles, most calls are done from home. So that gives us the option of using a cheap mobile plan with limited talk time.
For the mobile-only people: Back to the convenience of extensions all through the house - there are "landline" phone bases that you can buy that can be paired with multiple mobile phones over Bluetooth.
And you can use these w/o a landline/VOIP connection. When you come into Bluetooth range with your mobile (keep the charger near the '"landline" base - the base shown even has a USB charging jack), all cell calls will be transferred to the "landline", and you can pick up at any extension.
One example is:
https://www.amazon.com/AT-CLP99387-...=B073DNQ8Q1&psc=1&refRID=9DZ2E8GWNRT0J0N1WQR9
-ERD50