Honestly, it seems like a much bigger waste of resources when you buy a flash drive, or some dart flights, or a box of staples, or any other single item that fits in your pocket, and the store puts it in a plastic bag. So why do these laws only apply to grocery stores? Bags make sense when you have a lot to carry. But one item you can throw in your pocket? No need for a bag.
Do they? Most of what I’m seeing here says “all retailers.”
In my town, there was a proposal to only ban them in grocery stores. I didn’t realize it was different in California.
And I can tell you in the county near me that I no longer live in that has a bag ban, there is no active enforcement, it’s strictly “honor system,” however the 5 cent charge includes a couple of cents for the retailer so there is incentive for them to comply, especially for retailers that use the most of plastic bags, i.e. grocery stores.
Perhaps you need to get out more often? 
BTW, it’s always different in California.
In the town my store was in, the charge for bags (not a ban) first applied only to grocery type stores. It was I pilot program and grocery stores were the obvious source for most of the bag litter. The law was expanded to all retailers not to long after.
The reason for just grocery stores was mainly volume. Most other stores you probably only use one bag, grocery stores people walk out with a half dozen doubled-up sacks.
It’s all retailers in the one town in my county that ‘banned’ them. Actually, they have to charge 10 cents each.
I use 'em for lots of stuff. So I bought 5000 of them on Amazon.
Before the universal ban began the “grocery” store ban covered any store that sold food, such as CVS.
I’m sure not everyone checks, but the cashier at a bookstore in San Francisco told me that they got nailed for giving away bags.
And you can’t even buy the plastic bag - only paper ones.