Stores already had private label stuff; “Food Club” is the brand I recall at our local grocery store.
But the generic stuff was something else entirely. The ones I remember (1981 or so), would have had a stark white can that said “GREEN BEANS” on it. I also recall a six-pack of beer with white cans that literally just said “BEER”.
I suspect that it was the precursor to today’s multi-tiered house-brand system; at my local Kroger, you might find Barilla pasta, “Private Selection” pasta, Kroger pasta, and “Psst” brand, in that order of price, with the “Private Selection” brand intended to compete with the name-brand stuff, the Kroger-branded stuff being the normal house-brand stuff, and the “Psst” brand being the value brand stuff.
Otherwise, I thnk it was a marketing gimmick- they were memorable for sure.