Why does each state of India have a separate language?

Well, almost, each state…
And sometimes, I feel like I am answering questions on Quora… 🙂 but I love to find answers for questions like these.
Now let us try to answer the question, first though some introduction. Each of the four(or is it five states, now?) southern states of India – Tamil Nadu, Kerala, Andhra Pradesh, Telangana and Karnataka each have a separate language and there are other local dialects too… (amazing, isn’t it?! :))The Northern states mostly adhere to Hindi. The western state of Gujarat has Gujarati as its language and the eastern states of India have their own languages (Assamese, Bengali etc) India is stated to home to 23 official languages and another 1650 languages!! (can you imagine?)
India might be the only country in the world or one of the few countries that has so many languages. No sooner do we drive 5-6 hours(roughly – not perfect here) in India , are we in another state with a different language and entirely different customs and traditions. 

 
But how did so many languages come into existence in India? 
India is an old country with rich traditions and customs. It is shaped by a beautiful history from the Mughal empire, Ashoka empire, Hoysala empire and so on.  As each dynasty left, they carved out beautiful traditions and new languages. It mixed with local languages and new dialects must have been born. This might have passed down generations and ultimately that became the language of a particular area of land… till a new dynasty came to power. This is my thought to this question – what is yours?
The reason that the languages stayed for so many years and it is still living:
The only answer that came to my mind was that we could not move as much(new forms of transportation like cars, bikes, boats, air travel have been achieved only of late) – so the languages that mushroomed stayed where they were. Moving from one place to another is a chore even in this day and age – imagine how it would have been several years ago. 
So, if Tamil was spoken in the state of Tamil Nadu and if people could not move much, they stayed there and propagated the language there alone. The same might be the case for other languages too. This has been continuing till date and the beautiful languages of India have stayed, grown and have continued to embellish our lives!