1. Why did they grow into the issue in the first place? If this is a problem, it's a problem. Why do they have the problem? Something is obviously going awry, and the CAUSE is my biggest concern.
2. How do you know? Maybe they will and maybe they won't. You cannot guarantee they'll "outgrow" an issue, and then you will have #3.
3. Why wait? Why waste my child's growing and maturation time just watching a problem? Why not identify what the root cause is and go to work right away to ameliorate the issue?
Sometimes--not always, but sometimes--the "they'll outgrow it" advice comes from a lack of information about what to do about the problem. They don't have anything left in their tool kit to combat the issue, so "wait and see" is the bottom of the advice barrel.
If you are uncomfortable with your child's development, YOU ARE RIGHT. If you see your child falling behind their peers in social graces, academics or motor skills, don't feel ashamed about wanting to start work right away to help them. If someone tells you to "wait and see", then don't hesitate to get another opinion. Information is easily-obtainable in this information age---keep looking until you find what your heart tells you is right!
Then your child has a much better chance of "outgrowing" an issue because their parent is setting up the right environment/activities to support the brain in that growth.