I can't imagine anyone using the app to unlock their car on a normal basis. Normally, you just walk up to it with your phone with bluetooth enabled, and it unlocks for you(you don't need to proactively take an action on the app like clicking an unlock button)
So, you carry the keycard in your wallet in case your phone dies or it is stolen or whatever, you can still get in and start your car. But 99.999% of times you just walk up to your car and start driving without unlocking, or turning a key, or anything like that.
The keycard is just a back-up that you can keep in your wallet. Unlocking with the app (phone) happens automatically with bluetooth when you are near the car, no internet required.
The main reason to use the app is if you want to unlock remotely for someone else using your car.
So, you carry the keycard in your wallet in case your phone dies or it is stolen or whatever, you can still get in and start your car. But 99.999% of times you just walk up to your car and start driving without unlocking, or turning a key, or anything like that.