Why Allah Told Angels That He Is Going To Create Human Race
Angels have to deal with humans, therefore God told them he was creating a new creation. Since angels have intellect, therefore God informed them and cleared their doubts. This is because God is very considerate and it was His generosity.
They are connected with them. Some of them record their deeds, other run the affairs of the world, they protect them. They bring revelation to the prophets. They punished their deniers etc.