Alire: why, why, why?

I am new to Ada and all stuff around it and I learned that the primary tool used to build programs is GPRbuild.

I was nicely surprised that the syntax of the file describing how to buiild a program is clean and readable:

project Hello is
   for Main use ("hello.adb");
   for Source_Dirs use ("src");
   for Object_Dir use "obj";
   for Exec_Dir use ".";
   for Run_Path_Origin use "/";
   for Locally_Removed_Files use ("myfile");

   package Binder is
      for Default_Switches ("Ada") use ("-shared");
   end Binder;
end Hello;

Now there is a new package manager built on top of that - Alire.

It has all the bangs and whistles - it downloads, manages dependencies, prints out colors and emojis.

My question is: why are we using syntax like this

{'case(distribution)' = {
    'debian|ubuntu': true,
    '...': false
}}

# Or in a more idiomatic TOML syntax
['case(distribution)']
'debian|ubuntu' = true
'...' = false

instead of something like this

case distribution is
   when 'debian' | 'ubuntu'   => True;
   when others   => False;
end case;

Why pretend to have a declarative file format that becomes a very ugly programming tool?

Bird in flight: line drawing