I guess the benefit of lazy by default is that (given Haskell is an experiment in purity) it sets the expectation that things will be side-effect free by default.
Were that not a design criteria it might have been better to make things strict by default and have a "lazy" monad rather than do lazy by default and use monads for all the side effecting stuff.
Were that not a design criteria it might have been better to make things strict by default and have a "lazy" monad rather than do lazy by default and use monads for all the side effecting stuff.