You can use two Windows machines at once with a single keyboard and mouse without any special hardware. I had an extra laptop lying around that now connects with the same keyboard and mouse as my PC.

You can share a keyboard and mouse across multiple Windows and macOS computers, if you know the right tools to use.

Laptops are practical because you can take them with you. However, laptops have a relatively small screen. If you work on a mobile computer, it quickly becomes annoying to constantly switch programs.