Yes, it can happen that your interests become part of your career path. However, most people these days do whatever they can to make a living and earn money. Very few people have the option to choose their occupation in America now - they just do what they can, whether they are interested in that career or not.
Sometimes people's interests become a part of their career plans. But we are conditioned by society and media to think that money is the most important thing. People are more likely to pursue a career that gets them the most money than the most enjoyment. We feel that money is the only means by which we can pursue our interests however, we often become so wrapped up in making the most money that we forget to enjoy ourselves.