Home security requires it as well or you sign a spot on contract relinquishing liability due to cell towers down during blackouts and high crime situations. Dead cell on charger they cant reach you. They send the blue. If... it's a false alarm homeowner is charged $50 each time as cops tired of chasing false alarms all day. Cell is not always reliable.  We have to keep our landline for our HARDWIRED security system we own.