Why do Mexicans have more common last names than other Hispanic nationalities like Puerto Ricans, Cubans, etc.?

A lot more Mexican people I've seen share common Hispanic last names like Lopez, Sanchez ,Diaz,etc. But I've seen more Puerto Ricans, Cubans, white people from Spain, etc. with much more varied last names like Alcala, Nieto, Leon, Delgado,Pomales, etc. And of course you have last names from conquistadors... show more A lot more Mexican people I've seen share common Hispanic last names like Lopez, Sanchez ,Diaz,etc.

But I've seen more Puerto Ricans, Cubans, white people from Spain, etc. with much more varied last names like Alcala, Nieto, Leon, Delgado,Pomales, etc.
And of course you have last names from conquistadors like De Soto, Pizarro, etc.
Last names I never see among Mexican Americans

Why do so many Mexican-American people have the same common surnames more so than other Hispanic nationalities?
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