Why can't people buy puppies as soon as they are born, i own one and had to wait 6 weeks because it needed milk from his mom so is this true, and if so why do puppies need to be with their mothers for 6 weeks? *this is for a report so me out.

This is in fact true. You actually answered your own question. The reason is because they need to stay with the mother to feed off the milk. Just like most animals and even humans, they need to drink the mothers milk and develop their bodies more before they can consume solid foods.