Haven't been to the GM Volt forums in a while, but some things never change...
Whenever someone here says "I want to do A", inevitably, rather than someone saying "Here's how you can do A", there's usually a large onslaught of people who are saying things like "Why would you want to do A, when you can do B?", or "Only a fool would do A", etc, etc. It's maddening. Stick to the subject people! The OP wants a locking glovebox. I can think of perfectly good reasons someone might want a locking glovebox, even if it is easy to force open.
1) It's a legal expectation of privacy. Let's say you are carrying a large amount of cash for whatever legitimate reason. If you get pulled over in many US Counties, that cash can be seized (stolen) from you without ANY evidence of a crime being committed, under the pretense that it *must* be drug-money, leaving YOU with the legal burden of recovering it. (look up the horrors of civil asset forfeiture) By keeping it in a *locked* compartment, the police require a specific warrant to unlock and search your glovebox in addition to the rest of the car.
2) It is one more thing to slow down a thief. It may not slow them much, but it might slow them down just enough for them to ignore it and move on to the next victim.
3) To block access to certain items from your kids, etc..
4) To leave the windows down and have at least *some* layer of security for a few valuables.
I could go on...
Sure, there are alternatives to all of these, but where else does one get a conveniently locking container that is securely attached to the vehicle's interior? Locking gloveboxes have been a feature in almost all cars for as long as I can remember. Why GM abandoned them here is beyond me.