Frankly - how many phone calls do you really make and take these days?
It's vanishingly rare for me. I got a call from a friend today - but I think I otherwise only make or receive a legit phone call every few days. We use social media mostly. Work "calls" are on apps.
A family could probably get away with 2 phones easily, as long as they have home internet.
Now... When I was young and internet was over dial-up, having a single phone line for our whole family caused quite a lot of spats.
Actual voice phone calls are so rare for me these days that I'll often go months without making or receiving one, though my mobile phone is always with me.
And I recently realised that the house I live in, which was built in 2020, has no provision for any sort of landline telephone at all.