When they usually are people that don't bother doing anything for anyone else and are generally aloof and think they're brilliant?
Those that bother with people, make an effort and care about others get walked over. Those that walk over others, and have a high opinion of themselves get people absolutely falling over themselves to do things for them and to be their friend.
I'm beginning to think life would be a lot better if I focussed on myself all the time and didn't make an effort for anyone.