If people planned their shopping they might save money. People manage to take the right number of shopping bags, it really isn't that difficult to plan the number of tubs/reusable sealable bags etc.But... You need to make a decision to take the right sized tub, you need to plan what you are buying, you need to have enough tubs that you can be flexible with not running out of the right size, you have no choice of size as you would today. You have the money to afford to take tubs to the supermarket. Etc, etc.
Some people, for right or wrong, cannot plan their lives in that manner on a day to day basis.
A deposit system for swappable tubs for example wouldn't be expensive for the customer for example.
I never said it would suit everybody, but it could certainly work for the vast majority and would massively cut down on the amount of one use packaging/plastic that is polluting our planet.