The fact is that the well off in India come from traditionally "upper" castes. Linguistically speaking too (like English speakers), the caste correlation is quite strong. Even among the non-English speaking rich (like wealthy farmers in the rural areas), the same caste correlation pops up. In a country where upwards of 90% of marriages are within the same caste[1], wealth accrued to certain castes stays within them (a self-sustaining system). So it shouldn't be surprising to see caste used an explanation for inequality.
1. http://www.thehindu.com/data/just-5-per-cent-of-indian-marri...!