I think that most prime fighters do it, but many people at the end of their careers would. Someone like wlad could decide at this stage that he is about to retire anyways so he might as well fight in the Olympics to finish off his career.

There is a difference between amateurs and pro. Professionals train as a job. Most amateurs do it on the side. Also, even the amateurs that train a lot like ones from Cuba, they aren't training their punching power. Imagine Tyson who didn't make the Olympics decides to enter them in 2000. If he fought some kid from Finland, he may do serious damage. He wouldn't just be taking up points. He would put everything he had on those punches.