Why don't some masters read the eight characters of minors?

The eight characters are only seen from the Universiade, and everyone's age is different. As for before the Universiade, I used a child lock to look after the children. Because only children can see children when they are turned off. And the eight characters can't see the child's experience. Whether he can live to be lucky is still a mystery. If he can live to be lucky, he will tell fortune with eight characters. thank you