Because of the tax dollars (or euros or whatever) which the residents pay and the immigrants don't? Ok so you are saying the right to be anywhere should be given to anyone. Is the right to spend my tax money (which was used up to build infrastructure, institutions, healthcare, etc. etc.) also something that should be given to anyone else in the entire world? How can you possibly think this is just? That every random person should be able to use publicly paid infrastructure that they haven't paid for?