Such parents are emotionally and psychological immature. They have unrealistic and rigid standards as to what is acceptable and unacceptable. They are also unforgiving parents. They have the precepts that their children must be perfect or near perfect in any task they undertake. They see mistakes as somehow a mortal transgression. They also have limited perceptions as to what success means. To them, a mistake and/or failure may hamper, even doom a child for life. They do not want their children's opportunities lessened, even ruined because of a failure or mistake. They want their children to have unlimited opportunities so in their eyes that means very little, if any, failures or mistakes.
There are parents who believe that their children should be little adults. Such parents are intolerant of the fact that children are still developing and as developing people, they are bound to fail and make mistakes. These parents want a well-ordered universe and mistakes and failures preclude this. They have unreasonably and unrealistic high standards for their children and woe to the children if they fall short of such goals. These parents furthermore feel that their children's mistakes and failures will reflect badly upon them. So they relentlessly drill their children to be perfect, little adults in order for the former to have a well-ordered, smoothly functioning world. Also, they want their children to be the best and nothing less will do.