Depends on if you're using Monix/Haskell style tasks (lazy, run when depended on) or JS-style promises (E Promise / C# Task / Java Future - run when instantiated, waiting is post-submission). Agreed completely though, structured concurrency is fantastic.
To schedule tasks properly, you need to know who is waiting on them as early as possible. With a promise, you only know when you get to the "wait()" call, which is too late.
The correct solution is called structured concurrency.