Haskell: Why aren't infix type constructors allowed?

Question

In the Haskell 98 report, I found this:

The syntax for Haskell type expressions is given above. Just as data values are built using data constructors,

Answer 1

Just to be completely clear: Haskell 98 and Haskell 2000 both allow infix value constructors such as

data Complex r = r :+ r

Here the value constructor (:+) is infix, as in 5 :+ 7.

You only need the TypeOperators extension to have type constructors which are infix. For example,

data x ??! y = Left x | Right y

Here the type constructor (??!) is infix, as in Int ??! Bool.