TL;DR: the car battery was dead
But, there is a mechanical backup with an ordinary car. In my 2012 Volvo, I can open the driver's door with the mechanical key. If the fob is ded, I can physically insert it and start the car. If the car is also dead, I have to sort that out to drive it, obviously.
I like to MTB and I used to climb, so I carry a backup battery that can start the engine if need be. But I appreciate that with a ZipCar, the whole point is that you don't need to go somewhere and pick up a mechanical key. So it's really the same risk profile as if I were to drive around with the key fob, but leave the mechanical key at home.
The other worrisome thing is if a car is designed that it needs the Internet to start. If you drive it somewhere remote, you have a problem. Or if there is a service outage, you have a problem.
If I buy another car, it will probably brag thatI can use my phone as my key. I will still want to carry the mechanical key, but my phone will then become a single point of failure. With my fob, and my 2012 car, I can start the car even if the fob battery dies. But if my phone dies, I will be SOL.
Luckily, said backup battery that I carry in my car has a USB port to recharge my phone. But even then, what if the network is down? Am I to trust Bluetooth to do its thing?
These failure modes require some thinking through before going anywhere remote. I'd want to work all this out before taking another driving holiday with my family.
With an EV yes, but not with an ICE. Just keep a jump box in your trunk.
The benefits of having a spare "jump box" in the trunk are obvious, but it's important to remember that this means carrying a dangerous amount of energy in form that is a very serious fire risk if anything damaged the battery.
I'm sure there are many other fantastic reasons to want access to your vehicle when the battery is flat.
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.
I'm not hard core enough to have a pre-computer vehicle, though.
Europe has a much higher take rate on manuals.
This depends on just how dead it is on newer cars.
If it's able to run the electronics but just unable to crank enough to start, this can work. If it's dead enough that you can't unlock the doors it's probably also dead enough that the fuel pump, ECU, etc. aren't going to be able to do their thing.
Carbureted vehicles can be bump started from flat dead for the most part, but EFI and especially direct injected vehicles need some electricity to operate.
Edit: And upon reflection, maybe not. Because I'd have to pay someone to reset the computer.
Edit: But wait a minute. If the vehicle is moving downhill, and you engage the clutch in first gear, the engine will be turning. And even if it's not firing, the alternator will also be turning. So you should have enough power for the computer, ignition and fuel pump. Or am I missing something?
Also, are there cars where you need the electronics to disengage the brakes?
http://oldcarmanualproject.com/manuals/Buick/1953/Owners/ima...
This feature disappeared in the early 60s for cost reasons.
When a battery was on the edge of failure, I was also amazed at how many days it continued to be able to start for, driving a mere 3 miles per say and starting it twice. The voltage gauge on an accessory I had would show the battery under 10 volts, I'd push the ignition button and silence would follow, then seconds later the faintest sound of an engine would start. Every day, for nearly an entire month of winter.