Because they aren't the only invaders? Tigrex and seregios are examples of the other that are old invaders but aren't because they are either not in the game or can't inhabit certain areas in this case, the coral Highlands for no reason. Bazelgeuse and Regular jho too, they just aren't in high rank.
Also, just because they are invaders doesn't make them territorial, I mean, I don't get how going to different locales makes you territorial