Former MSFT here. People tend to think of Microsoft as one unified company with a unified strategy.
That is not the case, its best thought of as a batch of little companies that band together to create a product. These companies may compete for resources and attention internally and so each one will optimize for their own benefit.
Ads in Edge? That's probably a decision made by some Principal Program Manager with director support on the browser team. The metrics that get tracked for that event are likely how many people click through the ad, rather than the over all impact to the OS.
The OS Core team doesn't have the influence to say no, or stop the browser from showing those ads. I recall internally when I (a paying customer for O365) got a toast (that is what a popup ad is called internally) for O365 and I decided to raise an issue.
Some PM II (mid-level PM was running the campaign, and they were showing metrics that more people signed up for O365 as a result of the campaign, so per them it was good. I was not in that organization and since that director had OKRs that required signups, he told me to go away.
The core OS stripped down has none of these things, but at integrated build, lots of stuff gets put in, and when one team says no to something, often another one will say yes. A good example is that Office has its own update infrastructure and tooling outside of Windows Update. Why? Office wanted to deliver updates on weekly basis and Windows Update said no as that would be too impacting for users, so Office simply said ok and built their own.
These issues rarely if ever get surfaced to an executive, as by the time the metrics get up to a CVP generally they are showing broader trends, like adoption, or game breaking bugs, or as you note, the line going up. Executives do not get these problems (such as inconsistent UI) to them. Those things rarely rise above a Group PM or Engineering Manager level, and those people often do not care about the complaint as for that metric helps them or is part of their strategy.
Windows, the product team cannot do anything about it due to political problems internally at MS and that is not the engineering team behind Window's fault. We (as that was a team I was on) hated when a product team would do something obnoxious and if we could catch it prior to release would often bluntly complain. More often than not we would get told that we were the platform and to stay out of the other teams business.
Anyways, there isn't some mass company dark pattern strategy or other conspiracy, just a bunch of little factions that are all optimizing for their own interests. Office is probably the worst offender of the batch (Skype, Teams, OneDrive) and Windows can do little about it.