Because things like libqt6 aren't likely to be understood by Microsoft developers.
One thing, which Microsoft has really been successful in the last 30 years was GUIs. Their UIs were typically slick and efficient, and for each and every Microsoft GUI strangeness I can probably show you 10 worse GTK or KDE UX defects. Yes, Microsoft has a footing in boot loaders, they were also engaged in embedded platforms for a while (is WinCE still a thing?), but that's all beside the point.
If you look at typical code produced in Visual Studio, you'd expect a GUI driven DB connected Windows application deeply embedded in the Microsoft ecosystem. The classical "we support Windows 10 and 11 only" type application. One can easily imagine a code quality checker for such an ecosystem, which would fail miserably in a boot loader. I know, how the code checkers we use all barf up on our custom heap manager "oh noes the pointer arithmetic" "oh noes the int to pointer type cast".
If Copilot can debug WinAMP, then good. If you can aim it at uboot, then it can probably also deal with our heap manager. Well, at least once it goes beyond "oh noes, malloc(size+1)" type warnings.
PS: yes, I know from our kernel devs, that fuzzing and AI generated CVEs are a menace right now, and they typically appear right after (not before, when it would be a lot more useful) release, because this gives you higher street cred somewhere. If Copilot could condense these fuzzer and AI bug reports to extract their useful bits, then go Copilot. Haven't seen that yet, but at least I know, that Copilot has been trained on more than MS Word and WinAMP.