It sounds like from the forum that some people rely on only the app, and Tesla markets this as an option. Seems like a big issue to push that feature and then for it to be down for hours.
My phone battery lasts all day, and the internet is rarely down; but servers on the other hand...
An app is a great backup to have.
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.