Most (flagship) phones are rooted using an unlocked boot loader... in which case the "rooting methods" you're refering to is just a script to run a few commands to unlock the bootloader in fastboot mode, boot the phone into a temporary recovery system (which are by the way open source) and then use that to modify the OS. You can do it from a CLI yourself if you like. It's just time consuming. Most people just want the push button solution, yeah, maybe it's hacked together by some guy on a forum, but most of the solutions I've seen like that are just shell scripts in one form or another.