Rust is a language in active development, continually getting improvements and new features. Using Rustup is the best way of managing up to date toolchains (and multiple toolchain versions if you have to).

It's no harder than apt-get install, and sets the best practice early on so that someone doesn't get confused and have to switch later.

"curl | sh" is only an anti-pattern in the sense that you have to trust the source (and therefore "curl | sh" without https is bad). It gives exactly the same ability to execute arbitrary code on your machine as downloading an RPM/DEB does, or adding a vendor specific repo (e.g. Docker). Distro package repos probably have broader scrutiny of the contents of packages, but there are a lot of packages so how sure can you be?