Lots of reasons, but a big one is that dependency and build management in C++ is absolutely hellish unless you use stuff like Conan which nobody knows. In Rust, you use Cargo and everyone is happy.
Cargo is great, for pure Rust codebases, otherwise it is build.rs or having to learn another build system, and then people aren't that happy any longer.
But you are right, that this is some extra work for dev, so this is question of trade offs: do you want to deal with all C++ build tooling mess, or you are Ok to do some manual steps.
Another alternative is to use some popular stable linux distro as build platform, then many libs will be packaged as part of that distro.