They're not intended to be reused as garbage bags, you're supposed to SHOP with them - thus reducing the need for packing groceries into plastic bags. Here in the Bay Area (where Contra Costa County is located), we've always been ahead of the recycling game... I live in San Francisco, where plastic bags have been outlawed for
years. That doesn't mean you can't find them, shop owners just have to pay extra taxes for distributing them.
As for garbage bags, I don't buy them very often... I used recycled paper bags for recyclables, and small plastic or paper bags for non-recyclable garbage. We also try to compost here, so that stuff goes into a special compost bag - or directly into the green bin.