Your fellow adult diners are paying well for the anticipated culinary experience. A crying baby or rambunctious child seriously damages everybody's evening. I sympathize with parents who can't afford to have someone watch their children all the time. That's why God invented fast-food places. A quick reminder about behaving like a grown-up in the eyes of restaurant management.
Reservations are a contract.
You make them. The restaurant in turn reserves a table for you at the appointed time. Your job is to keep that reservation. If you can't, have the common decency to call the restaurant so that they can give the table to others. It may be difficult to grasp this, all of you who were raised to believe that the sun rose and set on your every activity, but no one other than your mother really cares about your latest diet, divorce or death of a pet.