[infectoid]

And having shelter from the rain while you wait for someone to arrive can be a great advantage.

I'm sure there are many other fantastic reasons to want access to your vehicle when the battery is flat.

[Bartweiss]

Yep, that's potentially a huge difference.

If you can't open the car, you probably can't pop the hood latch to get a jump-start, which makes the difference between a tow and a simple drive to a store. And "stuck alone at the trailhead with a dead battery" is nothing new to hikers, but being able to spend the night in the car if you have to makes it a lot more pleasant.