By making you bring bags, you're more suggestible! Giving small commands make you more likely to obey larger ones. This is well established for special needs children and ABA. If you have a difficult child with a learning disability who doesn't want to do something, ABA therapists will give them a simple command first as part of
behavioral momentum . So you want a kid to brush their teeth and they refuse?...try asking them to touch their nose first...then clap their hands...and weirdly enough, they're more likely to obey afterwards.
So if everyone else is throwing out conspiracy theories, I'll make up one...by telling shoppers they need to provide their own bag (in my town, you get charged a fee if you use a reusable bag), the retailers embraced this long before it was mandated by local ordinance because it is like ABA...Bring your bag...walk through the produce section to get to the dairy (you came for milk, but now you're thinking about fruit)...buy our special. My baseless conspiracy theory is that reusable bags make you more susceptible to following commands.