There are reasons.
- Inertia. I've always had one, so the habit is there.
- Totally free conference calling. When parents call, just pick up the extension. No need to burn double minutes, no mucking around with speaker-phone. Great!
- It gives us an 'us' number. We each have our own cells for getting each of us individually, but sometimes we need an us number. Like for the landlord, or utilities, or or or.
- It's yet enother number to put into PagerDuty. If I really need to get up at 4am, making that phone ring is a good way to do it, especially since it's impossible to put it to Vibrate or Airplane Mode.
- I share a house with a cell-phone resister. They have one, but only use it as a portable internet connection not a voice communications device. They'll probably drop the phone and go with an iPad and a SIM card when the time comes. That person will need a phone number.
Conference-calling, I tell you.