It's because Amazon's ad platform has been the best ecommerce ad platform for the narrow and profitable purpose of direct sales basically since the day that it launched. Google let Amazon take a giant bite out of Shopping because it was complacent with its also profitable business model of absorbing giant corporate black hole ad budgets and earning multi-hundred dollar clicks off of people like personal injury lawyers.
I just went through a rabbit hole of sites about adwords for injury lawyers and my mind is blown by how obvious and expected it is but it’s still insane to think of a single click being billed 200$. But it makes perfect sense, adwords is far more suited to for this purpose and it’s one case of everyone getting what they want (except the dude getting sued) so why not? Google is getting healthy competition in the ad space so within that dimension it’s great? If we now just ensure the Amazon workers can unionise and put amazons more physical manifestations on check then this is a better situation overall than whatever we have now.
I run a commercial insurance campaign with clicks from $25 to $45 each but it works and provides the whole company with enough leads the renew the next year to make it worth it but it costs $120k+ a year. Google has figured out how to make the organic list as irrelevant as possible.