Well, there’s many reasons, and it’s not all about keeping your shit together. There are plenty of nice assault rifle style bags, but you gotta watch what you order online because you might find out that little M4 Carbine you have in your gun safe won’t fit in a gun case that is designed for that barrel length. Your tactical flashlight, laser, optics and the list goes on can cause it to not fit in there. I’ve had to carry some of my Carbines in a Elite Survival bag that was really designed for a sniper rifle because my smaller AK type gun cases wouldn’t fit them. I took my flashlight on my LWRC M6A2 last week and tossed it in a case not realizing that the flashlight was floating around and could have damaged something.
Protecting your stuff can vary, if you want to drop it out of a helicopter, get and SKB gun case, but there are some fine gun cases like the Blackhawk gun cases that are really drag bags. These gun cases can carry pistol, pistol ammo, lots of AR15 gun magazines and more. It might be a good idea to research gun bags or better yet, stop in a gun shop that carries them so you know exactly what you are looking for. Having a gun bag that fits your needs may take some research because some gun bags an be pricey and ordering them online from just a picture can be a headache.