Because the ruling elite doesn't want a middle class. Middle class is wealthy enough to be free from control from them.
It's why the Elite is using lots of money to convince people to destroy the welfare state. To dissolve middle class in order to return to their previous exclusive rule.
Have to disagree with you there. The elite needs a 'middle-class' and always has done. After all, who is it that has provided the bulk of the doctors and the teachers. The accountants and the small businessmen. The middle managers, the lawyers, and the higher ranks of the police. The 'elite' is reliant upon there being a middle class to help service its needs, otherwise it would be unable to survive.
Seeing how Republicans act in regard to teachers' wages, they want teachers to be lower-class.
I don't know for UK (I suppose it's affected by NHS), but doctors are clearly upper-class here (some are gaining over 300,000$/year). My family owns a small business, and there is considerable pressure to be integrated in big corporations. I don't know about UK again, but here, many lawyers are millionnaires. It leaves the upper police, middle managers and accountants, which doesn't account for much people.
