Occam has exactly this. SEQ executes statements sequentially. PAR executes them in parallel, though the language is based on CSP and Cooperative Multitasking, so the idea of it doing 'the right thing' with a PAR is a little different.

Think of Occam programs as big Factorio factories.

https://en.wikipedia.org/wiki/Occam_(programming_language)

Alot the ideas that came out of Occam and CSP have been brought into various coroutine libraries though. Kotlin Coroutines, Goroutines, etc. So its definitely something that is explored.