Let's see, Upper Class chooses the degrees because the parents want their children to succeed. Middle class does it because its what they can afford and Solidly Middle Class do it because it was "enough for them".
Some parents feel the choices their children make will not net them the future they want, they set the guidelines and only stray from the chosen degree if it interferes with something very serious in their lives, such as constantly sick or allergic to animals.
This is seen often in different cultures and sometimes not. People often want to become what their parents are, because of the notoriety, success and knowledge the parent has, this plays a large part in what decisions are made and for who.
Hope this helps.