Earlier quoted context omitted.
If you're asking why Microsoft's advice is to format and reinstall, well, consider who it's coming from.
Because you can upgrade from windows 3.11 all the way to 10, good luck with ubuntu. Yeah, I see your point.
That has never ever worked for me until the 7 -> 10 upgrade: 95 -> 98, 98 -> 2k, 2k -> XP and XP -> 7 all failed miserably and required installing from scratch.
And even 7 -> 10 failed without any helpful information= the first few times I tried it (unlike OSX where I've been upgrading and migrating the same system for more than 10 years across multiple machines and versions).