Have you ever thought that maybe this is just how people connect with each other now? I get where you're coming from but I kinda like it when folks share their random cooking tips in public, it feels less like people telling you what to do and more like they just want to have a friendly chat. Life gets so automated these days that a stranger giving you a tip about your burger patties seems like a nice little moment of real human contact.
Three different times this month random strangers have given me cooking tips while I was just minding my own business at the grocery store. A woman in the meat aisle told me to add a splash of pickle juice to my burger patties, then a guy at the farmers market insisted I put cinnamon in my chili. Your beer can lady fits right into this pattern I keep noticing where people just cannot resist sharing their kitchen secrets with strangers in public places.