Why are spoilt people so horrible?

It's not really their fault, they never got a chance to learn the same lessons that we did when they grew up, most people are taught to wait for christmas/birthday to get presents (learn patience), share their toys with other children (learn to be cooperative), do chores to earn their pocket money (learn the value of money), not get everything that they want (learn to appreciate what they have). When parents don't do this with their kids, they think they're being kinder but really it stops them learning some vital life lessons which are harder to overcome as an adult than when they were a child