There could be many reasons for it. First of all, today's world is not good. There are many people who can show them the wrong way. There are Kidnappers also. The Second thing is that let suppose one of them is very disciplined and a intelligent boy, but if he gets the habit of going to cinemas, then his whole life would be changed. He would not be interested in studies rather in movies, shows etc. Parents always think good for their children.