No, it doesn't have to be on WordPress necessarily. You can use Squarespace or Wix or whatever you want. But I generally recommend people start on WordPress because it's affordable, open-source, and there's a huge support community out there. There are a ton of themes & plugins you can customize your site and make it exactly what you want. And If you decide you really wanna grow it into a blog later on and try to get search traffic, it's going to be much more search friendly if you're on WordPress.