What are mini backpacks good for? We buy big backpacks so we can put more stuff in. But why would we buy mini backpacks when crossbody, sling, or shoulder bags are handier? Mini backpacks have straps for both your shoulders, so the bag is balanced on your back. Bending your body one way can damage your back. Also, mini backpacks are great for concerts! You don't have to leave them behind at the baggage counter.