The Rust community also takes semver quite seriously. 0.1.0 can break API compatibility when it moves to 0.2.0, so prototypes that want to iterate on API stay pre-1.0 until they feel confident in their API. The Cargo ecosystem has shockingly few 2.x or 3.x versions.
By comparison to the long tail of the C library ecosystem (SONAME handling), and the package ecosystems of many other languages, most of which do not use sufficiently well-defined versioning schemes to allow expressing dependencies like "1.4 or any compatible version". In other languages, I've done the equivalent of "cargo update && cargo build" and encountered build errors due to API changes. In Cargo, I've found that exceptionally rare.
