I don't know why that would be anyone's preference given that if you used telnet to connect to a remote shell, ^] is the default escape character. So using ^[ to exit input mode is dangerously close to popping you out of your telnet session. Someone who claims to have used vi for 25+ years (get off my lawn, ssh didn't exist back then) would have likely used telnet and been bitten by that more than once.

I didn't switch to Ctrl-[ until sufficiently recently that anything I'm running vi-ish things on is over ssh.

I will, however, never forgive Excel for Esc being "abandon edit".