1. In India, for years, since the ancient periods, the SCs, STs and OBCs were deprived and exploited. So now, when we are a independent and democratic nation. Its very necessary that every citizen should get equal opportunities. This is what reserved constituencies ensure. The deprived classes often lack proper resources to contest in elections, in such cases the more influencial candidates prevent them from winning elections. That's why constituencies are reserved so that our parliament isn't deprived of the voice of a significant section of our population.
2. Man power isn't assessed in terms of human numbers. A single person who is very powerful and influencial may be far more valuable than a huge group with insignificant power or qualities. Our political system provides a good example for this. The loksabha constitutes of 543 members on whole, but the cabinet only 20 or so. Still the cabinet, although a part of loksabha only is more powerful than the general loksabha.