Well, what would you do instead? It's an interpreted language. When you type "foofunction" at a prompt, you don't want it to wait around in case you define that to have meaning later.

You probably want the interpreter to be smart: "Am I loading a script from a file, or am I receiving instructions interactively on the command-line?" But now there's two modes of execution, and code in a bash script won't work if you type it into the prompt yourself. That's a bit uncomfortable.

I really hate writing things in reverse, but a decent style in Bash is to put everything in functions, w/ a main() at the top:

    #! /usr/bin/env bash
    set -e -u
    bar='bar'
    
    main() {
      foofunction
    }
    
    foofunction() {
      echo 'foo'
      echo $bar
    }

    main "$@"

C is the same, but at least with C it's possible to declare functions before providing definitions. Is it possible that it's the same in bash?