Because it's not important. The industry does not want pros risking their careers for such a team.
Just like the Little League World Series, we don't send our best kids, we send our best town's all star team instead of a complete best of the country team.
When was the last time you saw a chubby kid on the DR's team or the Japan national team? We should hold a separate LLWS after our United States teams crown a champion, then send OUR best players (taken from the entire country and not just one town) to take on these other countries, then we'd show what we can do. We may not win, but we'd do a damn sight better than we do now.