The concept of a condom used as a water bag in a kit is simply based on the idea that it takes up the least amount of storage space for the amount of water that it will hold. To get the water out depends on the style of closure. You can tie a knot in it but will probably break it in the untying. Tie a piece of cord around the neck. Then untie, drink and the retie. If the name bothers you think of it as a balloon or substitute a balloon.

That answers the questions. Personally I myself prefer othe style contiers. The deciding factor is ruggedness over compactness.

We also must remember that when the inclusion of a condom as a water container most of the modern products refered to did not exist. No zip loc bags or other collapsable containers. In most cases the only other things available were rigged containers and most of the were metal. Those containers were far larger than the kits themselves..

Progress as made more options available.