Why a camera bag

There is good reason for purchasing a well designed, thick-padded camera bag with compartmentalized storage and secure lock-down of equipment stowed in it.  Today, I took two lenses with me and my SB-900 flash.  I wanted to take a few photos of some rooms of a building at work.  Nothing artistic about it--I just need a couple of photos for a project.  So, I brought my lenses and the flash with my D7000 in the picnic-bag-turned-into-camera-bag bag.  I started shooting a room and decided that my bag could be in the way so I lifted it off the table it sat on and moved to lay it on the floor.  As soon as I started lifting the bag, a stomach wrenching feeling came over me.  A familiar sound was heard a year ago today.  My SB-800 crashed into the floor and broke into two pieces.  My SB-900 took its turn today.  It flew out of the bag.  I was relieved after collecting the batteries that got ejected out that except for a minor scuff mark, nothing apparent happened to the flash gun.  I should use a real camera bag.