Ask HN: Why is Mac still easy to backdoor?

This link describes the process: https://null-byte.wonderhowto.com/how-to/hacking-macos-configure-backdoor-anyones-macbook-0184637/

What I don't understand and why I'm asking this is, why isn't this patched? Should this be patched? What possible value or reason is there for it to be so easy to hack a mac not using filevault?

It appears that a firmware password prevents this problem. If this is so, then why isn't a firmware password more widely known about and encouraged?