SC, ST and OBC are socially and educationally backward. Their backwardness is the result of social disability imposed upon them through a well-organised social structure of caste and ethnic superiority. Free and undiscriminated access to social life and its benefits like good employment, good education, social relation (contacts) that you come to make during education and employment especially are vital for an individual to achieve the fullest they can in their life. The reservation in certain jobs and academia, thus, provides them the opportunities to make up for the social injustice done to them.
In the book Constitutional Law of India from Dr. J. N. Pandey, the Indra Sawhney case (aka Mandal case) is summarised and mention this et al:
6. A backward class of citizens cannot be identified only and exclusively with
reference to economic criteria.
To identify backward classes exclusively with reference to economic criterion would defeat the very object of Article 16(4) to give adequate representation to backward classes in the services. Article 16(4) is not aimed only at economic upliftment or alleviation of poverty. It is specifically designed to give a due share in the state power to those who have remained out of it mainly on account of their social and therefore, educational and economic backwardness.
That said, Executive differs from Judiciary on this account and has argued for their backwardness in the Statement of Objects and Reasons of 124th Constitutional Amendment Bill, 2019:
At present, the economically weaker sections of citizens have largely remained excluded from attending the higher educational institutions and public employment on account of their financial incapacity to compete with the persons who are economically more privileged. The benefits of existing reservations under clauses (4) and (5) of article 15 and clause (4) of article 16 are generally unavailable to them unless they meet the specific criteria of social and educational backwardness.
The directive principles of State policy contained in article 46 of the Constitution enjoins that the State shall promote with special care the educational and economic interests of the weaker sections of the people, and, in particular, of the Scheduled Castes and the Scheduled Tribes, and shall protect them from social injustice and all forms of exploitation.
However, economically weaker sections of citizens were not eligible for the benefit of reservation.With a view to fulfil the mandate of article 46, and to ensure that economically weaker sections of citizens to get a fair chance of receiving higher education and participation in employment in the services of the State, it has been decided to amend the Constitution of India.
Whether EWS meets the criteria of backwardness would be best judged by Supreme Court, when challenged, so the contradictory views are the only foundations upon which the debate continues on that Bill and the issue.