I'm not your parent, but the overall point of this kind of thing is that all of these individual steps are more annoying and error-prone than one command that just takes care of it. `cargo build` is all you need to build the vast majority of Rust projects. No need to edit the Makefile for those headers, or remember which commands you need to install the various dependencies, and name them individually, figuring out which name maps to your distro's naming scheme, etc. It's not just "one command vs five" it's "one command for every project vs five commands that differ slightly per project and per platform". `make` can come close to this, and it's why people love `./configure; make`, and there's no inherent reason why this couldn't paper over some more differences to make it near universal, but that still only gets you Unix platforms.

> but on the other hand you don't end up in a situation where you need virtual environments for every application because they've all downloaded slightly different versions of the same packages.

The real downside here is that if you need two different programs with two different versions of packages, you're stuck. This is often mitigated by things like foo vs foo2, but I have been in a situation where two projects both rely on different versions of foo2, and cannot be unified. The per-project dependency strategy handles this with ease, the global strategy cannot.