I don't think it's utterly ridiculous for most people. It's very common here in the Netherlands and I'm not sure the average Dutch person is so extremely peculiar to the rest of society. It's really no more inconvenient than carrying the bank card I need to pay for my purchase and in the worst case scenario if I forget it I can just buy a new bag to reuse with my other items.

Regarding how clean they are, I just wash mine in the washing machine and I wash my vegetables as well.