Your question is about Indian police force for whom I have not only the least respect, but even have hatred. The police force was trained by the Britishers to suppress the people so that they can rule easily. Unfortunately, that highhandedness of the police still continues. For them, male, female, children or even overaged people are like animals. Day in and day out, I see news of police atrocities on TV in various states. A number of times, I had even emailed Chief Minsters of the states where such incidents of police atrocities were reported by the media. I do not know what happens to such emails. I never received any reply of any of my emails. We, Indians, have to learn courtesy of replying the emails that we receive from people. My experience with American senators is just the opposite.
Coming back to your main question, the fact is that most of India's problems, be it terrorism, naxalite movements or many other criminal activities have their root in the irresponsible actions of our police force. Most people join such force so that they can amass wealth by torturing people. They even bribe to get such appointments and there are rates of bribes for getting posted at more lucrative locations where they can get earn more money.
If people suffer at the hands of criminals like a family member getting murdered or committing suicide, police immediately swings into action and traps the relatives with the sole purpose of extorting money from them. Aarushi murder case is a glaring example of how parents were held responsible by the police in short time without sufficient proof and by creating a hypothetical story. Besides the suffering of the family tragedy, they had to undergo torture and social humiliation due to inhuman conduct of the police force. I had seen a debate on tackling naxal menace on TV in which there were participants who had first hand information on the source of the problem. Unemployment in the area, lack of development, acquisition of farmers' land by the government in the name of establishing industry in which they do not get jobs but suffer due to pollution created by such industries and above all heinous crimes committed by the security stationed there of committing rapes and beating up innocents were reported by the participants of the debate. Recent refusal by the government in giving licence to Vedanta is because government has, of late, realised the problem. Illegal mining of valuable resources from lands of the people who keep suffering results in revolt with arms.
I keep getting sidetracked in answering your question. "What is the use of such FORCE (Police)" is a question appropriately asked. Police is no friend of the people and for any problem, they are not even the last to approach. Never approach them. They can only harass you and solve no problem. All the time, they keep thinking of how can they make more money and not on how can they do their duty effectively so that people will have respect for them.
Unless Police Reforms are done to such a great extent that the parents of children in India who today think of making them engineers and doctors think of making them police officers, things cannot improve. Standard of morality has gone down all round. Judges were caught copying in some written exam of their subject. Many of our politicians have huge Swiss Bank accounts. One Chief Minister even owns mines in a foreign country as reported. When all such news are reported and no action is taken by the government, what can you expect from police force or even anyone in the government?