Got a pair of these, one for the wife and one for me.
While they're not going to turn a car wreck into a holiday brunch, the number of things carefully packed into this tiny little vinyl bag is pretty impressive.
All I added to it was a printed list of the most important phone numbers and addresses I have. Because it sucks to have access to a phone but no idea what number to call because you've gotten used to having your cell dial for you.
When things go wrong, you rarely have warning. If you have to leave work, home, DEF-CON or your charming vacation home for any reason, it isn't good to have to figure out what to pack. A bug out bag solves that problem. You put whatever you have to have in it and you don't mess with it, except to rotate out whatever might get stale or expire. What needs to be in a bug out bag?