Zig is still under active development, and new releases often introduce
breaking changes. This makes updating the default version of zig easier.
Some packages did not receive this change because they could be using
the c compiler or linker of zig, which doesn't receive as much breaking
changes compared to e.g. the zig std library.
https://github.com/NixOS/nixpkgs/pull/248243#discussion_r1289401340