Preferring marriage within the same cast has to do more with having partner from the same cultural/family norms and practices. You see, Indian society is quite old (thousands of years); there are lot of customs re ways of worship, deities, dresses, eating/etc. that have evolved over this period and people (mostly parents) prefer a match in that regard. Because mostly marriages are arranged by parents (though in cities at least, love marriage has also become a common place thing.)

And if you talk to Americans, many of their parents would not accept if they came out as gay. That doesn't mean human rights are not advancing in the US, it just means that the previous generations have a hard time letting go of their bigoted beliefs.

Whoah there, I didn't say there hasn't been progress; I was asking a question in relation to "the concept of caste is almost invisible", because several Indian friends from different cities have told me otherwise