Last I checked India was over 1 billion in population with sky rocketing political corruption stats. How does these missiles benefits majority who go without a proper meal everyday.
Pride.
To tackle the political corruption issue will require a massive movement and a big consensus. If you visit India, you will realize that nothing gets done through consensus. Only individual actors achieve large successes. India still lives in a kingdom mindset where people draw pride from the acts of their superiors and are thankful for such acts. If you try to do something radically different, you will get a lot of resistance from everyone around you because "that doesn't work here". But if you do succeed, everyone around will claim to be part of it and will talk of you proudly.
So, in that environment, building an ICBM (which is btw a very hard engineering challenge and took India 30 years) is an achievable goal for an individual actor (the defence organization DRDO) and because it was an Indian success, brings pride to a nation of 1.2 billion. Getting rid of corruption will make our lives significantly better (there are many other much more modest goals that will have a similar effect), but it won't bring close to as much pride. In a country where you'd die before driving a Tata Nano if you had any semblance of money (Tata Nano is seen as a cheap car - something not to be proud of) and an iPhone is a must have, such sources of pride as an ICBM count for a lot.
Yes, we are flawed, but as we say, "what to do, we are like this only"
One of the main strengths of india is it's ability to create very low cost products of reasonable quality in many fields.it's probably the greatest thing modern india can offer the world.
For example the tata nano has created the whole mini car segment, that has significantly reduced the cost of low end cars around the world. now many people globally can afford to buy new car. Such effect is much harder to achieve than building an ICBM(which is a pretty old technology).
And indians don't take pride in it(if not at a level of buying it, but at least as a national innovation) ? that's a
shame.