I agree!

You're mistaken if you think Haskell users don't take advantage of state or side effects. They do, you just don't understand the difference.

Try this course:

http://www.seas.upenn.edu/~cis194/lectures.html

Then see LYAH's section on the State monad:

http://learnyouahaskell.com/for-a-few-monads-more

Then reflect on ST:

http://www.haskell.org/haskellwiki/Monad/ST

Then this example using mutable variables and closures:

http://bitemyapp.com/posts/2014-03-25-when-nested-io-actions...

Side-effecting closures mutating variables!

It's not "no state or side effects".

It's about making state and side effects typed and explicit so they can be properly composed and manipulated.