Well I just like being able to switch team members on the fly instead of rebuilding them from the ground up (might be because I am new to Competive Pokemon, so I like being able to experiment easier)
It's silly to hate simulators. Even if you do want to breed your own Pokemon on the game cart for that sweet satisfaction, it would still be worth it to test the team out on a simulator so that you don't spend so much time making a team that doesn't work in the end.