I am on a 10+ year old Laptop with Slackware, for desktop use it is just as fast as any modern Laptop with Windows, I would even say it is faster.
Also you will find Libreoffice is just as good as M/S Office. Just ignore the fud. FWIW, I believe many foreign countries will start migrating to Linux and I heard that is already happening in China.
I have two, sadly.
1. I use my Windows PC for flight simulators. While many simulators will indeed run under proton, the hardware devices (VR, joysticks, throttles, pedals, panels, etc.) usually will not, or at best run with minimal functionality.
2. I develop cross-platform software and need a Windows PC to test that environment.
A third for some people:
3. There is no great alternative to certain visual media software. e.g. Affinity Photo/Adobe Photoshop has no equivalent on Linux. No, GIMP is not anywhere near equivalent- in the same way that Nano is not equivalent to Visual Studio Code.
I've read online that people have attempted to use wine in order to emulate the Windows environment with no success.
Old Intel based computers are terrible for power usage. Modern computers that are ARM based are much better for the environment.