Up until recently, most of Indian farming depended on (and still does to a good extent) on Bulls ploughing the fields for seeding. That and bullock carts as transport.

That answers my question then - they get castrated and used for transport.

Bulls make more cows?

You only need one to impregnate lots of cows.

I wonder what happens to the male offspring of Cows in India?

not if you want a reasonably distributed gene pool, diversity of genes is always a good idea

Well, yes. You don't want one bull to do 100% of cows, but one bull can easily do an entire herd, and using In Vitro methods the most valuable bulls fertilise thousands of cows.