The thinking is that MS' needs come first, and yours are way, way down the list, unless you're a volume license holder. Whereby, you get an off switch.

So the magnitude or logic of the gain doesn't factor much unless a policy hits the news with a stickiness of several months.

They don't need a lot of conversions. If 2% of users take them up on the ad, that's an increase in revenue and profit. If it pisses off 40% of users, that's not a problem, because only 0.001% of users are going to get so angry that they'll stop using Windows (and those users probably paid for a license anyway as part of the computer purchase, so it won't affect MS's revenues).

and it's a pool not paying them for services so they probably don't care about losing them.