Why do I have to be home to turn on my VOiP phone?

Episode 1254 (2:06:26)

Cristina from San Diego, CA

Cristina is getting rid of her landline and wants to use VOiP. But they insist someone be there during the service. Why? Leo says that is because landlines have independent power. Cable phones use VOIP. When the power goes out, the internet goes out. So they need to install a backup battery to power the system during an outage. She's also concerned about cutting the copper. Leo says they could and often do that, even though they aren't supposed to.