The important part is to engage newcomers. This is easiest to do if there is no barrier to playing with Haskell. They can always install Haskell once they're a bit more familiar with it and see why it's awesome.

If you're already planning to learn Haskell and have a book about it, this is useful because it lets the author of the tutorial integrate the material more closely with the language environment. This makes things like little exercises to illustrate a particular point easier to do.