Nobody is telling you that you MUST use Linux, but it helps you. In many situations Linux can be much better for you than Windows or mac OS. Being a gamer or using a specific software that can't be run on Linux using wine won't help you when replacing the operating systems but you can use a dual boot and start Windows, for example, when you are playing a game or using that specific software.
For the moment you can find out more about this tiny Core Linux that is a magical modern Linux distro that can run on literally a potato. Because you can also run Linux on an older computers that you have used to run Windows and you can't do that anymore.
You can see the video here.
