Who are you going to call if there is a fire? What if you live in an apartment building?
Stay in contact with friends and family when the cell towers go down.
The Landlines work when the power is out, and they're cheap. You probably have one in your closet. If not, your local store typically has one.
Get a old school corded one, not a cordless one that needs charging or power.
It cost about $9 to have, and your internet provider probably sells it already.
I'm surprised FEMA didn't list this in their recent Tweet.
^ this. OP literally is using a VOIP phone. That's technically not a landline (POTS) and of no use if the net goes down and power goes down with it.
Hah. I'm glad you've surveyed my phone system already and know what I have installed. ;P
You're point is clear though. It's best for each end user to clarify what they have individually and proceed accordingly.