The tiredness: players in real life are never tired. The stamina concept doesn't exist, it should not exist in tennis video games. It does have an impact over the course of a tournament, but not during a match.
Oh, maybe you should tell Andy Murray, David Ferrer and Gilles Simon that their playing style has always been harmless then
Perhaps I got it wrong, but if you want to tell us that players don't get tired during a match, then just try and play tennis, you should notice by yourself