The Case Against Bags

My new computer came with a free backpack which is on sale this week on eBay. There are tons of computer bags available these days, but they all look the same.
Actually, there are some original designs out there. It is annoying though, that no one seems to understand the difference between a case and a bag, I want a hard-shell case for my computer. Not a fabric and foam bag. Shouldn’t the case be stronger than the item which it purports to protect?