[kibwen]

In this case the Future trait puts the "standard" in "standard library" by providing an agreed-upon interface by which third-party crates can interact without conflicts. There's a high bar for adding new modules to the stdlib, and fundamental building blocks like Future are far, far easier to accept than, say, the entire Tokio stack.

Note as well that Tokio isn't the only library that can be used here, there's plenty of experimentation in this space.