When military units are in the field, they are up contrary to a lot of challenges besides just the enemy. They must undergo harsh conditions such as extreme heat, bitter cold and torrential rains, and they must sleep whenever they get a chance, no matter what the conditions. When it comes to sleep gear, the biggest challenge is to make the most of comfort while still keeping it light enough so that one person can transmit everything he needs on his back. This is true in the military as well as in recreational outdoor adventures. You can also check the army surplus bags at online stores.
Backpackers have comparable needs to soldiers when it comes to being able to carry all of their equipment on their backs, which is why army surplus goods are so popular with backpacking enthusiasts. When you're walking many miles into the wilderness, you need to be equipped for every eventuality and safeguard that you aren't going to be left lacking simply because you left some items behind to eradicate excess weight.
If you're out in the back woods and get hit by a freak snowstorm or spell of cold weather, you're going to wish that your sleeping bag was appraised for sub-zero temperatures. A simple trivial insulating emergency blanket can fit in anybody's pack, taking up minimal space without adding extra weight, and it can offer added insulation in case of unexpected cold.