Except that that's not actually true either; I don't pay for Debian.

Indeed, advertising and data collection is ultimately there to drive a profit in real money - at some point, someone still has to put actual money into the system - in advertising, this is typically from consumers buying the advertised products. If everything turns into an advertising platform with no actual way for real money (as opposed to "engagement") to get into the system, it will fall apart.

However, the same kind of people who are willing to sacrifice long-term brand trustworthiness of a previously-reputable OS supplier in exchange for some quick "engagement" metrics to justify their salary and/or promotion will be in other companies paying for these ads and then finding a way to coerce the data/metrics to justify that ad spend, even though in the long term none of those ads may actually bring net profits to the company.

As long as there is enough money being available from previous profits and/or other sources, both of these camps will independently cooperate with each other to further their own careers at the expense of their respective companies' long-term outlooks.

They're paying for it with a slightly more expensive laptop/computer price. The manufacturers don't get Windows for free, they ultimately pass that cost on to the consumer.

Very few? Most machines sold have an OEM version, which I'm sure was paid for by the OEM (Dell, HP, Lenovo, etc)