It's a matter of habit, I guess, but. - Ctrl-[ is a chord that you have to press with 4/5 fingers using both hands at once. - Whereas jk/fd etc are next to ea

It's a matter of habit, I guess, but. - Ctrl-[ is a chord that you have to press with 4/5 fingers using both hands at once. - Whereas jk/fd etc are next to each other on the home row and pressed with 2/3 of the same hand sequentially. Given the number of times you would have to exit insert mode, the second option is arguably more ergonomic...