Well, you could also loose your keys.

A lot of newer tech products seem intended to move us to a place where we don't need to carry separate wallets/keys alongside our phones. That's a reasonable goal.

Look at how popular credit card phone cases are!

I would never, ever, rely on just my phone battery for access to my car.

Ok but other people might?

Ok but the question isn't whether it's a good idea. The question is how much it harms tesla owners. It sounds like this might significantly disrupt people who only use their phone and I wouldn't be surprised if a decent number of people made that(poor) decision.

I love my credit card case. It fits three cards and doesn’t feel bulky. It says “silk” on the back so that must be the brand.

I edited that part out, you're right their are some relatively nice ones! But, it would be comparatively slimmer without the cards!

or even more likely: the battery dies.