Parents who don't want their children dating set this restriction for different reasons, most of them are either an irrational fear of something happening to their child (which really just hold the child back because, whether you like it or not things <em>will</em> happen) or because of religious reasons (in that case.. you shouldn't date).
Most parents just want what is best for their child and even more so when they're "protecting" their only child. The problem with this is, through dating you learn what you like and don't like. You learn what you want and how to deal with certain things. Some parents tend to hold their children back from seeing the "dangerous side of the world" only for them to be thrown into it when they're adults and living on their own. In this case, maybe the mother wanted her son to reach a certain age before dating, or she wants him to date a person he can see versus online dating.
