I mean really! Can't people just like, ugh, not need to carry so much stuff!
Timbuk2 Lex Large or X Large. Both of them have serious hauling portage and are are built tough. I have the large Lex backpack. Good for an urban environment where a mountain pack is impractical or just too big.
If you have a week's worth of groceries and you're more a mile's walk from the store. Carrying home the stuff in both of your hands isn't really an appealing proposition. You may need to ferry more stuff than you think and extra cubic space always helps!