I agree this does happens, however I've seen too many instances where this is not the aim.

Often, two people fall in love from different backgrounds and it completely destroys them knowing their parent would never accept.

Are these people just plain selfish?  Why go into the relationship in the first place?  Aren't we humans and not animals, can't we control our urges and feelings for the sake of respecting and honouring our parents?

(Not my view, just a thought)