"Being broken" has many forms, and numbness is just one of the outcomes that can come from it (it's even listed as one of the symptoms of depression). Numbness is a coping mechanism that strips someone of both the good and the bad from becoming convinced on a subconscious level that you're better off detached than feeling things, which usually is done either from bottling or detaching. Bottling will break a person while detachment rids them of the ability to have good or bad feelings.
There's other coping mechanisms too, such as becoming delusional. Delusion at least allows someone to enjoy themselves still, but that cost involves losing touch with reality.
"Isn't it more liberating for any course of action to be the same, you can do whatever you want."
It's empty and boring when there's fewer differences between your experiences than there either ought to be or used to be. Being able to feel bad about something allows you to feel just as good about something else, while blanding your emotional spectrum takes away from all dimensions that don't have to do with survival (fear and aggression), and with further progression it could even bland those.
How good or bad something is comes from how much you let it affect you. If you cannot be affected by things, then nothing feels like anything. Why do anything if you can't even appreciate it?
"To me, numbness is something that develops out of a realistic view of reality."
A person however can have a realistic view of reality without becoming numb, it just takes more effort on the part of the individual to be able to cope with that truth. It's easier to convince yourself that you "don't care" or "shouldn't care" than accept that you do and move on.