Rand, uuid, and no built in logging implementation are three examples that require crates but probably shouldn’t.
No built in logging seems pretty crazy. Is there a story behind that?
println!() exists but there are more fancy crates like http://lib.rs/tracing and https://lib.rs/crates/log
Rust's standard library hasn't received any major additions since 1.0 in 2015, back when nobody was writing web services in Rust so no one needed logging.