They may have other duties related to the team as well, like going to meetings or watching films about the opposition. Athletes often move to the place where their team is located. If management decides to trade them, they may have to move again. At least in team sports, professional athletes often have curfews and other restrictions on what they can and can't do in their personal lives. They can't just leave the job at the office like workers in other jobs can.
Most professional athletes spend a good part of their lives practicing their sport.
Basketball players, for example, often recall having spent hours and hours working on their dribble or jump shot. Ice skaters may practice several hours a day all week long. Playing organized sports at an early level can only help. Most professional athletes played their sport in both high school and college. Schools usually require that students have good grades to play on their sports teams.