Why Would Anyone Want to Leave Cuba?

Cuba is considering canceling their participation in the the amateur World Boxing Championships in Chicago in October. Why? Because Castro doesn't want his boxers to defect.

According to Micheal Moore and his supporters of Universal Health Care, Cuba is a far better place to be than the US. Why would Castro even think these ungrateful Cuban athletes would want to defect. Aren't Americans defecting to Cuba in droves now that Cuba's health care secret is out?