Plastic bags are the genital warts of litter -- they're incredibly widespread, nearly impossible to get rid of, and can lead to much worse problems down the line. The only thing that works is prevention -- i.e. not using them in the first place. But the plastics industry doesn't take too kindly to that. Here's a sampling of the tactics the industry has used to keep people from weaning themselves off plastic bags:
Lobbying (to the tune of millions of dollars) against legislation that would ban or put fees on plastic bags at the local level.
Trying to trade bag recycling plants for the promise that there will be no bag-banning laws. Trying to recycle plastic bags tends to just break recycling machines, so this isn't a very good deal.
Filing lawsuits against manufacturers of reusable bags.
Filing lawsuits against local governments that ban or limit plastic bags.
Spreading misinformation about the dangers of reusable bags, i.e. that they can contain bacteria.