I've got a Lifeventure one that I've had for about 20 years - it converts into a very light rucksack so is ideal for taking on a long remote solo ride and then deciding on the way back that you might get pick up a few bottles of beer. Plus it is good to have a carrying solution should you happen upon a Calvatia gigantea. It's true that you can fit a lot of stuff in jersey pockets, but I don't like them to be overstuffed, and if I'm carrying food I like it to be proper doorstep sarnies or pork pies and and not some vile gel thingy.