When I was young, we didn't wear backpacks to school. We had book bags. And us boys would have "book bag fights," slamming our bags at each other.
Now, even adults wear backpacks, like little children.
So what?
A back pack is a great way to conceal a SBR in 5.56 or 6.5mm w/o anyone being suspicious for personal defence. With room left over for a tablet, lithium ion power bank and cables for your phone’s.