For coroutines to be really useful, they have to be stackful. The guy that originally did the proposal for C++ is also an author of multiple coro libraries and did research on this. You can emulate stackful coros with stackless via trampoline, but heck, you can emulate stackless coros with closures and trampoline too! The requirement of this extra trampoline makes their use extra convoluted and negates the very slight advantages that such functionality may really bring.
Making stackful "right" was hard, so a useless compromise was made, which is basically like adding a syntactic sugar to the language.
It may be a compromise, but what exactly makes it "useless"? A similar style of async has been in use in e.g. C# for over a decade now, and it has been very successful there. Yes, it is syntactic sugar - but so are e.g. lambdas. What matters in practice is that it makes some kinds of code much shorter and easier to read.
stackful coroutines is a feature that is on par with power of delimited continuations (proven fact in academia, you can easily find somewhat easy to follow papers on this topic), stackless coroutines is a stupid gimmick. You see the "compromise"? You have argued to have a case to add a car, but after long debate, politics and "compomsie" you got a TOY car instead.
Theoretically everything is possible with a NAND gate, so the question is badly formulated from the beginning. There is a sibling comment from @jlokier who did a gread job of providing a sane summary, and not just some incoherent rambling like I did.
