My soap at home is similarly target's in house stuff. Half the things I buy from Costco are Kirkland.
Why do I do it? Because it's like half the price. Just like buying say AmazonBasics batteries vs Energizer.
Every CVS I've been to always has the CVS brand pretty much right next to the major label brand - they're equally accessible. If I ask a store worker where the shampoo is, he'll point me to the shampoo aisle where the CVS and major label brands are side-by-side. Contrast that with Amazon, where (at least for me) searching for "batteries" returns AmazonBasics in the top non-sponsored position.
Amazon - the shoppe - is the one making the decision, and it’s decision is to default to the item that Amazon manufactures.
In one instance the payor is choosing a manufacturer and the shoppe is fulfilling the order - all manufacturers are on equal footing; in the other the shoppe is both choosing the manufacturer (itself) and fulfilling, while disadvantaging the other manufacturers, and making the decision without asking the payor.
I hope you see how these situations are in no way analogous, and only superficially related in that the customer ends up with a knock-off.
Think of it from the brand perspective. CVS pays you to stock their product on their shelves, so while they compete with you, they also send you money every month regardless.
On the other hand, you have to pay Amazon to include your products in their catalog. So while they compete with you, you pay them for the privilege. And everything you do to innovate, they steal.
They're always trying to push Prime (and to a lesser extent their video and music service) which represents extra clicks to sale. It's a significant auto-renewing commitment, not a $5 casual impulse add-on-- repeatedly dangling it in front of me and hoping I misclick into it borders on a dark pattern. I'd love to see a big one-click "I am not interested do not bother me further" button.
Everything about their checkout funnel is contrary to modern best practices. Fields are oddly arranged compared with most other ecommerce sites, and once you reach a certain point, the normal navigation disappears. I guess this is designed to trap the user with no way out but purchase, but it makes it harder to compare items, especially when you're trying to find out on shipping (see below).
Shipping is a mess to deal with. "You need to spend $25 for free shipping, but these items don't count". "These items can ONLY be purchased with an order of other items that hit the free-shipping threshold." "These items can only be purchased with Prime." There's no easy "estimate shipping" button without going several pages into checkout. These sort of complexities probably are engineered to steer customers towards buying the items fulfilled by them to avoid the pitfalls.
I'd also wonder if their brands "accidentally" do well because of how bad their product categorization is. Nobody else is selling AmazonBasics products, so the single listing gets all the ratings and sales volume. Meanwhile, the name brand has 30 slightly different poorly arranged listings all overlapped.
When I order an air purifier, amazon reminds me I might need to buy extra filters, stuff like that. many times i have ordered stuff from websites, and key components that make what i ordered useful were not part of the order.
That's a strange interpretation. Their checkout flow is as little as 1 click and their incredible growth is from only caring about the customer and delivering value better than anyone else. Many people do almost all of their shopping on Amazon because it's fast, easy, and reliable, even if the prices aren't the best.
Most retail works exactly the opposite - the manufacturer pays the retailer significant fees for shelf space.
Meanwhile on Amazon, brands pay Amazon to feature their products. Then they pay Amazon to stock/fulfill their products (FBO). Then they pay Amazon to feature their products (promotions).
Amazon is in a heads-I-win, tails-you-lose position vis-a-vis brands.