Just wondering. Did you buy windows 10 pro disk and install from that, or did you upgrade from Windows store from a free upgrade of 10?
You needed a licensed Windows 7 or 8 in order to upgrade; that one costs money too. You weren't able to get entirely free upgrade. It was more of exchange.
Again, not justifying the add- but I wouldn't be surprised if its because our accounts were at one time linked to home.