Let me make a small example that may illustrate the issue.
You can download the NetBSD source tree and compile it with any reasonable c compiler, whether you're running some sort of BSD, macOS or Linux. Some OSes have much older gcc (Red Hat, for instance), some have modern gcc, some have llvm. The source tree first compiles a compiler, which then compiles NetBSD. It's an automatic, easy to understand, easy to audit, two step process that's really nice and clean.
With rust, if you want to compile current rust, you need a pretty modern, up to date rust. You can usually use the last few versions, but you certainly can't use a version of rust that's even a year old. This, to some of us, is ridiculous - the language shouldn't change so much so quickly that something that was brand new a year ago literally can't be used today to compile something current.
If you really want to bootstrap rust from c, you'd have to start with rust from many years ago, compile it, then use it to compile newer rust, then use that to compile even newer rust, perhaps a half a dozen times until you get to today's rust. Again, this is really silly.
There are many of us who'd like to see rust be more directly usable and less dependent on a chain of compilers six levels deep.
That was back in 2018. Today mrustc can bootstrap rustc 1.54.0, but current rustc version is 1.80.1. So if the amount of steps still scales similarly, then today we're probably looking at ~26 rustc compilations to get to current version.
And please read that while keeping in mind how Rust compilation times are.
You can download the NetBSD source tree and compile it with any reasonable c compiler, whether you're running some sort of BSD, macOS or Linux. Some OSes have much older gcc (Red Hat, for instance), some have modern gcc, some have llvm. The source tree first compiles a compiler, which then compiles NetBSD. It's an automatic, easy to understand, easy to audit, two step process that's really nice and clean.
With rust, if you want to compile current rust, you need a pretty modern, up to date rust. You can usually use the last few versions, but you certainly can't use a version of rust that's even a year old. This, to some of us, is ridiculous - the language shouldn't change so much so quickly that something that was brand new a year ago literally can't be used today to compile something current.
If you really want to bootstrap rust from c, you'd have to start with rust from many years ago, compile it, then use it to compile newer rust, then use that to compile even newer rust, perhaps a half a dozen times until you get to today's rust. Again, this is really silly.
There are many of us who'd like to see rust be more directly usable and less dependent on a chain of compilers six levels deep.