Is it necessary?
Religion started as a way of organising people's beliefs about nature and about themselves. Everyone has an inner moral censor, no doubt, but most of us weaken and modify it, because its repeated accusations are a hindrance to our normal activities. But this can't continue ad infinitum. There has to be an external reference which is never changing, never heeding to our queries for modification. This is because whenever we want do something wrong, the first thing we do is change our mental censor to allow us 'this time alone'. Soon, this becomes a habit and we weaken the censor to the point where it no longer can prevent us from wrong actions. If and when this does occur, there has to be some other authority to save us from this valley and take us again to the plane of normal living. This was (and is) the job of religion. It was a reference, a handbook which clearly tells us what is good and what is not; what can be done and what shouldn't be. This is the primary work of all religions. The religions differ among themselves in lots and lots of ways, but there is no religion in the world which doesn't have this good/bad handbook (in whatever form it may be).
Unfortunately, however noble the aim of religion is, it falls in the hands of people who have other (not-so-noble) purposes. Just for the sake of an example, take Christianity. It was a wonderful religion when it was originated, with the followers being asked: "do not resist an evildoer. If anyone strikes you on the right cheek, turn to him the other also. (Matthew 5:38-39)". But soon, the emperors saw the potential power religion can give them, and started misusing it. This is, for the most part, the reason for atheists being present in large numbers in Christian countries. They see the wrong side of the coin - they see religion itself as having been created by power hungry people to rule over other people.
Somehow, India, and hence Hinduism didn't have such rulers (for the most part). In fact, there are lots and lots of cases where the reverse happened - emperors giving up kingdoms for the sake of religion, princes denying kingdom and moving on to forests to 'realise Him'. As a result, people never felt that religion was ruling over them. Moreover, the chief symbols of Hinduism were the monastics, who lived on whatever people gave to them, and blessed them even if they gave nothing. As a result, most saw religion as something that can give them a lot taking nothing away. This is perhaps the reason why religion is always accepted gleefully by every Indian - it is in their genes.