Why evaluate heredity vs environment?

Celia Green writes about heredity, intelligence and education. She makes an interesting point about the beliefs people hold in regards to heredity vs environment and their relation to government intervention:

One may wonder why it is of any interest to attempt to evaluate the relative importance of heredity and environmental factors on functionality. It only becomes of interest, surely, when opportunity of various kinds is not paid for directly by the individual, or his parents or guardian, but supplied by the state.

At present, many people, or at least many among the most influential, seem to wish to believe that there is no such thing as innate ability, and that there should be equality of opportunity (and hence equality of outcome). But what are we to understand by equality of opportunity? In practice, this is taken to mean that resources should be applied lavishly to those whose performance is below the average. Thus children with ‘special needs’, for example, are to be sent in taxis, accompanied by social workers, to special schools. And, although this is less explicitly advocated, those who are far ahead should be held back.