Your neighbour has a large extended family that fight all the time half the family push down your fence and move in with you demanding food shelter money etc
You
A.give them what you have?
B.call the police?
In a modern connected world you can not sit back and do nothing leaving country,s to become rogue harbouring crime finnancing terrorism etc
In the Uk you have a naturel border uncrossable by most, other countr,s dont have this luxury.