They want us to reuse bag, why store clerk pick on me?

It's because you could put something in the bag and it would look like you had already paid.

They now sell green baskets that you can take in and put your food into and you can check the food out and take them home in your green baskets.

The stores are just taking advantage of how easily people are fooled by greenwashing. The actual carbon footprint of the reusable bags tend to be higher than that of the disposable bags but the reusable bags help keep the litter problem down. Of course, it's technically the same people who littered when the bags were disposable.

It is to discourage people to use polythene bags.

You should carry , non polythene / plastic bags .

Like GenL Said, you should keep buying things in trolly or basket until the billing counter.

Either they will help you to put things in your bag or you have to do once the billing finishes.

There is no mandate that you should only carry non polythene bags.

You may take any bag on your interest. It is absolutely your interest in which way you want to carry your items.

It's for security reasons. When you use a cart, the items you are shopping for and you put there are "visible" up to the point when you reach the checkout counter but, if you put them in a bag, before you check out, it could be perceived as shoplifting...almost as if you put them in your pocket. That is why stores have rules like that.

I face it the same thing once.