What's the driver?

What should be the driving factor? Should it be career opurtunities in your place or should it be driven by the individuals interest? I am not sure how many of you will agree with me that in India we generally go by the career options available. I too have done the same.
But thinking now I sometimes feel that I should have gone by my interests and not by the career opurtunities that are there. I have heard a lot about foreign countries where people go by their interests. I have heard people telling me that one day a person may be a truck driver but another day he might be in the IT department of a company. Another instance which I heard from my colleague, he said that he met a person in Hawaii who is currently a tourist guide in Hawaii but before this he was a programmer earlier.
In India, now everyone becomes a Doctor or an Engineer. Not many people consider other options like for example Forrensic study. I never knew that such a course existed until I visited Madras university along with my friend once.
Like for example if we take Stephen Robert Irwin he could have taken a job just like anyone else, but he went by his interest to become a Crocodile hunter. I feel he has acheived something in his life by being someone distinct during his times. I admire him a lot. May his soul rest in peace and his family be given the courage and strength to overcome this huge loss.
Is money the only driving factor for us? Should't we value our interest also while deciding upon the profession that you want to choose?

Varta...