You're not exactly beating the system. That's just plain old brand loyalty, which companies love. You've stopped shopping based on quality or value, and they can turn a profit without investing anything into marketing.
However... you don't know what the brand is. The brand may be the store brand, which... while it's brand loyalty, is almost always the cheapest, and usually don't have any marketing expense beyond the product in the store in the first place.
I've learned to love most store brands, and... it may be my mind rationalizing it, but I think they've actually become much better quality wise than they were 20 or 30 years ago. But again may be a trick of the brain.
Biggest issue I see is that store brands often don't have the same level of variety. Chips - store brand may have 4 flavors - other vendors may have 10-12 on the shelf above. If I really want a specific flavor, I'll get a name brand, otherwise, just go with store brand (or.. with chips, hopefully skip altogether!)
One place that I can't quite find a non-brand name replacement I like is laundry detergent. I've tried the cheaper brands, store brands, etc..., and always end up back on Tide.
I remember reading that many of the costs of the in store offers and promotion are actually pushed to the supplier. Leaving Tesco, Asda etc on same margin as before. I suspect this hits smaller suppliers disproportionately.