Focus-stealing, too! Especially bad with Microsoft products. I can picture exactly what happened: a thousand complaints of "I lost a window in the heaping mess of open work on my desktop" each turned into a ticket to add Just One More focus steal until the first minute of a Microsoft-powered desktop's existence is various projects fighting in a brawl to repeatedly steal focus from one another.
It was a major win for the internet that it took this power away from the application layer.
Problem it isn't an API, it is just unexpected consequences of how a few things work. Fixing this just isn't easy as the simple attempts will break even more than the frustrating thing you are trying to fix - and thus be worse.
That said, Microsoft should have fixed this long ago - it is hard but a few people can do it given a few years to work through all the special cases.
Not just frustrating, it's a security hole. Stealing focus means a user may expect to be typing a password but find it's inputted somewhere they did not expect.
It was a major win for the internet that it took this power away from the application layer.