You are thinking narrowly. Lets say your profile is "environmentally conscious family man". If you just bought a Tesla, and for 3 weeks after all you saw were ads around the internet reinforcing that "teslas are good for the environment", "teslas are great for budding families". Those ads are designed to generate brand loyalty.

In a completely different context, ads can be used to reenforce status. That was a separate distinct point gp was making. If you want to buy luxury goods, but can't afford them, a well placed gucci ad can act as a brand anchor & keep you yearning.

Your point stands, that the "mega retarget post amazon ads" are a flaw in the system, but as the system gets more data, they will be tweaked to be more effective.

Amazon has plenty of data already to fix this - they undoubtedly could determine "purchasers of X don't buy another one for Y months on average afterwards" - and I remain baffled that they haven't.

This specific case - "here are some other vacuums you didn't buy" - is one that seems more likely to hurt my brand loyalty and post-purchase feelings than anything else.

So, in the other-branded vacuum case, I can see a reason: buyer's regret.

Chances being that anything that irks you about your new vacuum are going to be most accutely felt in the initial period.

So reminding you heavily that there are other, greener-grass vacuums out there seems productive in inceptioning "I'll never buy X brand again!" resentment.

Yeah but you can turn that argument each way, it's just reasoning backwards. It amounts to just doing whatever with the tracking data, waiting for something positive to happen because of it, and then claiming it.

They can do that with random data and it'll work just as well. It's called divination and you don't need to track me for it.

Amazon doesn't care if your loyal to the vacuum brand. They just want the purchase to be through them. If you are unhappy with the purchase they want the rebound sale.

I can't speak for an individual ad I haven't seen. Even if I did see it, I don't necessarily know marketing enough to analyze it. I just know that the purpose can be broader than your post was originally giving it credit for.