These things really do not have an actual reason. Take for example the Nic people who go to every project with a bash script that uses #!/bin/bash and tells them to use #!/usr/bin/env bash. There is no justification for trying to fix every bash script in existence over the operating system being able to resolve what the "current" bash version should be (/usr/bin/env already has to pick a version). This is pointless O(n) busy work Nix people have created for themselves when an O(1) solution exists.