performance - Why are scala Vals not lazy by default -

i have noticed exclusively use lazy val assignments avoid unnecessary computations, , can't see many situations 1 not want (dependency on mutable variables being notable exceptions of course).

it seem me 1 of great advantages of functional programming , 1 should encourage use whenever possible and, if understood correctly, haskell default.

so why scala values not lazy default? solely avoid issues relating mutable variables?

the big difference here between scala , haskell scala allows side-effects whereas haskell not.

laziness results in sorts of problems in language allows side-effects @ arbitrary points in program, order in side-effects take place becomes non-deterministic.

nearly transparent java interoperability plays large role in design of scala, , java libraries typically full of side-effects.