>>I have a couple of bags in my laptop bag and always carry a reusable folding bag in my jacket. We have a few in the boot of the car. That accounts for 90% of time I might need one.

you must shop frequently.

I shop 1 to 2 times a month, and buy a large qty when I shop. I absolutely despise going to the store. It is not uncommon for me to need 20+ bags per shopping trip

When I go there are also often people that with 2+ carts, having had to wait in line behind such people using the reusable bags it increased the check out time by a factor of at minimum 2, and sometimes 5x what would be normal due to people attempting to shove as much as they can in a limited number of bags, and they often times have far fewer bags than are need which delay's everyone as they mess around with moving things to maximize space