The common argument for a language feature is for standardization of how you express invariants and pre/post conditions so that tools (mostly static tooling and optimizers) can be designed around them.
But like modules and concepts the committee has opted for staggered implementation. What we have now is effectively syntax sugar over what could already be done with asserts, well designed types and exceptions.
But like modules and concepts the committee has opted for staggered implementation. What we have now is effectively syntax sugar over what could already be done with asserts, well designed types and exceptions.