Typically I dislike having to be forced into a package manager's version of a given language. For example I recently upgraded ansible on my old MacBook and brew decided that it had to install its own version of rust which meant compiling it from scratch. 12GB later and I got ansible installed. Yuck.
Likewise I've found CPAN to usually get out of my way… but at least in FreeBSD land I've not had to fight perl packages too much. And I've definitely been missing having Perl in the FreeBSD base system recently.
And if you don't install the third party rustc from out of repos your rustc
is only able to compile code written $now till about $now + 3 months.
If you're not doing things that rely on nightly you generally get a lot more than three months. The catch is, of course, that a lot of things depend on nightly.