[pishpash]

This is true, it's very unsanitary if you put unpackaged goods in there or get leaks.

Lots of stores also don't ask and give you a bag at whatever the locale's imposed fee is which they keep it, so there is an incentive to do this.

At the end of the day, the externality should not be captured by the store, but should be refunded back to the user with even distribution.