std is intentionally a minimal library rather than a "kitchen sink and everything else" library. Users are expected to import functionality from the crates.io ecosystem. There are a number of reasons for this choice that have been documented repeatedly in this forum—hence forum search is strongly suggested.
Those reasons include two facts:
items needing special compiler support must be in
std, which then requires that
std be maintained directly by the already-overburdened compiler team. (That's why each version of
std is only compatible with the identical version of
semver past-and-future compatibility guarantees for
std preclude any kind of breaking-change improvements
Other crates in the crates.io ecosystem do not suffer from these limitations, so by design they are intended to be the "go to" place for most functionality that doesn't require special support within the compiler.