Because operational semantics (of contemporary computers, at least) are very different from a simple denotational semantics. We have to bridge that gap: 1) Ei

Because operational semantics (of contemporary computers, at least) are very different from a simple denotational semantics. We have to bridge that gap: 1) Either use a compiler that hides away the operational details 2) Or use a language that directly maps to the operational semantics, but then is necessarily far away from the denotational ones