Imagine having a BBQ in your back yard, and a bald eagle lands nearby, looking to be fed. At this point, due to hunger, it would be very aggressive posing a danger to both you and to the eagle. Imprints also know nothing about territories. If they flew into the territory of another bird of the same species, they would not understand the other bird's calls. This could lead to one or both of the birds being injured or killed.
Predators are another problem.
People pose a tremendous hazard to birds, yet imprints have no fear of humans. Unable to recognize other predators they would not have the necessary defensive precautions. This is why imprinting is such a problem, and why, if you ever find a baby bird out of its nest, the best thing to do is leave it alone or to put it back in its nest if possible. Birds cannot smell, so there is no risk of parental rejection. Please do not try to take on the responsibility of raising a young bird.