That's somewhat of a copout. A child's behavior is influenced by a number of factors, most importantly the parents, but it's not entirely out of their control. And it's not an either or situation to travel with rowdy kids or not travel at all. Many times a parent just sits and yells, ignores or worse, hits the child. I've traveled extensively with children from 6 months through adolescence and never once did they act out or misbehave without instruction and repercussions. For the most part they were pleasant polite diners and travelers. More importantly, now that they are adults, they find those activities as adults infinitely more enjoyable.
The problem is that the state requires a minimum set of skills to operate a motor vehicle but not to procreate.