That you've asked this question means you don't understand the actual reason to do this. I might have my own bash in my home I use to run all my shell scripts, why are you ignoring my environment and going for the system shell? Unless you control the system or are writing a system script this is absolutely unexpected and bad behaviour. On macOS now that zsh is the main supported shell plenty of people run a modern Bash out of their home.
> plenty of people run a modern Bash out of their home
Ah, got it. Another failure mode. There is a /bin/bash, but it's an ancient, crummy thing, that is difficult to upgrade. MacOSX does this, so users paper this over by installing a private copy as ~/bin/bash. Thank you.
