Not sure I agree with that. I actually bought a duffle so it's easy to commute on public transport which actually requires a bit more walking. So a proper waist strap would be very nice to have. Add a couple of wheels on the bottom in case you feel like wheeling it around. And I reckon that would be a really sweet duffle! So who's gonna make it?
Blank Bats produced a duffle (pretty compact but big enough) which has wheels which is a bit of a USP. Must admit though, they didn't get much use from me as I found the top strap a bit short to pull the bag easily. However, the bag is very easy to carry, even slung over one shoulder on short journeys, and has a wealth of pockets. I can get a full kit in mine, including helmet, plus two bats, and it's compact enough to fit in the boot of my late middle youth (No Swearing Please) car.