You do see them. But the juveniles are just as big as the adults. They grow this big before they leave the nest. You would only see the tiny hatchlings if you found a pigeon nest. They have to be adult-sized (though they are young) before they leave the care of their parents. They grow up really fast, by the way. This is why the pigeons you see around are all big. Some of them are young ones, and it’s just hard to tell the difference when they are all the same size.