Some people have a family, or otherwise time consuming personal lives, which does limit the ability to learn new things outside of work. I wouldn’t really blame them for not ”bettering themselves” if they don’t get to do that on paid company time.
I enjoy being the dumbest person in the room. Others find it threatening.
And for those who are so busy outside of work that they can't grow inside of work, I feel for them because that sounds like an exhausting life.