It's a formal model that we can opt into surfacing, or subsume into convenient pre-packaged idioms. For engineering purposes you want to be aware of both. It's

It's a formal model that we can opt into surfacing, or subsume into convenient pre-packaged idioms. For engineering purposes you want to be aware of both. It's way easier to make sense of why it's relevant to write towards a formalism when you are working in assembly code and what is near at hand is load and store, push and pop, compare and jump. Likewise, if the code you are writing is actually concurrent in nature(such as the state machines written for video games, where execution is being handed off cooperatively across the game's various entities to produce state changes over time) most prepackaged idioms are insufficient or address the wrong issue. Utilizing a while loop and function calls for this assumes you can hand off something to the compiler and it produces comparisons, jumps, and stack manipulations, and that that's what you want - but in a concurrent environment, your concerns shift towards how to "synchronize, pause and resume" computations and effects, which is a much different way of thinking about control flow that makes the formal model relevant again.