What has been done with the windows for many years without any problems, does not seem to have arrived at many doors yet. There is always a sealing problem that shouldn't exist at all.
Anyone who has ever lived in an old house with doors without seals knows that this can be unpleasant. Apart from the fact that cold air trains and smells can get through, you understand almost every word that is spoken in the room when you are standing at the door. This is also what it is all about when a seal is mounted. For example, a fire-proof door must be smoke-proof. This not only brings something in case of fire, but also does not allow any other draught.