I promise this is a genuine question and not a Windows hit piece.
Every Windows computer I've ever had has slowly gotten laggier over time until my impatience has forced me to reinstall the OS to get the speed boost that comes with a fresh copy. In the schools I've worked in, computer labs and carts full of Windows machines have slowly sunsetted, becoming wholly unusable over time. I think Chromebooks have taken over education in part because they have a snappiness to them that sticks around for a long time, unlike the decay demonstrated by Windows computers.
In my current job, I was issued a Windows computer and a Chromebook at the same time, when I was hired. The Chromebook is still chugging along just fine, but the once fresh and quick Windows computer is now ramping down. I know it's not because of startup or background programs latching on over time because I don't have admin rights and thus can't install anything! I'm not a power user either. I really only ever run a browser with minimal tabs, along with the very occasional instance of office software and/or PDF reader. That's it. And what used to be instant and quick is now like... trudging... through... sludge...
Is there some fundamental design flaw in Windows? Am I finding a pattern where none exists? Do I not have enough experience with other OSes to know that this is true for them too? I'd love someone's insight on this topic.