Because I don't want to trust Microsoft more than I have to. It'd be the only non-distro provided keys on my computer. I would subject myself to them. Maybe in

Because I don't want to trust Microsoft more than I have to. It'd be the only non-distro provided keys on my computer. I would subject myself to them. Maybe in 5 years they decide that to download, you need a Microsoft account login? This weakens one of the core strengths of GNU/Linux, that every software installation is only an apt get away. Also, Debian packaging does a level of vetting that the software complies by their packaging policies, which ensures that it is truly libre. I know that Microsoft has their UEFI signing keys in all the IBM computers around the world and has signed the desktop Linux bootloaders as well, and I respect that they do this, but that's a different part of the stack. I understand that some entity needs to sign the bootloaders, and Microsoft has since shown itself to be a reasonable guardian.