Groceries were still doing this into the early ‘90s, but it wasn’t free anymore. It was just earning a discount on an encyclopedia volume every week.
They also used to give away silverware sets a piece at a time. You could also get dishrags or drinking glasses in boxes of powdered detergent. And then there were S&H green stamps.
We have similar freebies now, but it’s “join our loyalty points program and earn” or credit card points. Kohls cash, gas discounts, etc.