If you had asked a thoughtful question such as "Do you think people should control their kids better in a restaurant?"; or perhaps "Do you think parents have lost the ability to raise well mannered children?", then I could answer one of those questions.
Do you see the similarity to the way you asked the question, and the way the children you seem to keep running into behave in restaurants? (Tom Joad may have had a point in his reply!)
We eat out quite frequently. I can't remember the last time I saw a "bratty kid" in a restaurant. I've seen some real gems of kids, who make me smile just watching them. I've seen some kids who talk in a loud and animated way, but there are smiles around the table and the family looks happy. I've seen some normal amounts of 'having a bad day'. We all have them.
This is not to say that you haven't had a very different experience. If you are truly seated near "brats", that is unfortunate and I'm sure it can ruin a dining experience!
The worst thing for me to see is parents who seem somewhat abusive to their kids and are looking at the children like they totally hate them. I sat behind a woman on a plane once who kept telling poor little 3 year old Jeffery that she was going to beat his ***. I wanted to cry by the time the plane landed. Jeffery didn't bother me at all, it was the mother!
You can't change other people, you can only control yourself, the image you project to others of who YOU are, and your reactions to situations. And, you can raise your own children well to help make the world a better place. :)
I wish you good luck in seeing the good. As Craptacular mentioned above, this could just be bad karma.