That's really the only reason. Armstrong, Hincapie, etc. were already racing internationally when they were your age. Lance raced in the junior World Championships as a teenager, raced in the Olympic Games at age 21, and then turned pro right after that. Practically every other bike racer that you have heard of will have a similar level of experience. Your chances of making a living from bike racing are really pretty minimal. Don't give up your day job.