Because the citizens and those that came before them have the history of the building up the country that has fostered a good standard of living, rights, environmental standards, etc.
It is unsurprising they feel they are more entitled to the benefits than those outside the country who did not. It is a complex situation but that is the general gist.
So they have the right to a good life because they always had a good life?
I can understand that such thinking is convenient, but especially those who are afraid of outsourcing haven't done that much "building" at all. And how come that in virtually any other regard competition and free enterprise is enshrined, even to the detriment of poor people and low income workers, but not when origin is concerned?
For me this entitlement does not follow immediately from some kind of ancestral rights.
It is unsurprising they feel they are more entitled to the benefits than those outside the country who did not. It is a complex situation but that is the general gist.