Then why didn’t they do that on a regular basis knowing it will protect their users?
Why doesn't Windows or any other tech company do it. It's unnecessary to do it unless you are updating your firmware. This is NOT a huge problem for the vast majority of Mac users who the CIA and NSA couldn't care squat about. I doubt there are more than a few hundred compromised devices in the world, or they would have popped up on the radar of the anti malware labs by now.
Angela Merkel's compromised iPhone was found because it wouldn't update properly. . . As I've commented on other threads about the issues with this working on modern iPhones.
Also, Apple CLOSED this Mac Firmware vulnerability sometime last year before this ever came out and made it impossible to revise Firmware from any of these ports.
If you think your Mac's Firmware has been compromised, you can download an official version from Apple and reflash it yourself. Problem solved!