I agree it’s a good idea to carry your card in case your phone has a dead battery, or is lost or broken. However you do not need the Tesla network to be up, to use local phone-key features. So long as you have your phone in hand and bluetooth is on, just open your car door (by pushing the handles). The door will unlock. You can drive it away. No card swipe required. Even if the tesla network is down (which is rare).