When I was a kid, the supermarket had an isle named "generic", and all the generic stuff was relegated to that isle and came in plain yellow packaging. Back then, I would have accepted that they're not selling to the same customers as the name brands.
Today, store brand stuff at the supermarket is sitting on the shelf right next to the name brand stuff, with intentionally similar packaging. They are absolutely competing with the name brand stuff. And thats true at Home Depot and Walmart and Costco and everywhere else I shop that has a mix of store-brand and third-party brand stuff.
Of all the places I shop, Amazon is the only one whose store-brand is plainly labeled as such, and I give them kudos for that. Some places like the grocery store and Costco have a single store-brand, so you don't have to work too hard to figure out whats name brand and what isn't. While yet other places have several store brands that aren't really marketed as such in an attempt to confuse you into thinking you're getting a name brand (plumbing and electrical fixtures at Home Depot and Lowes is where I've seen this most rampantly)