why do we use the article" the" for neatherland but not for other country names?

Question

Answer

We must use the definite article "the" before countries which are in the plural form. 
For example:
the Netherlands, the Philippines, the United Arab Emirates. 
Similarly, we use the definite article "the" with the countries which have such words as:"Republic"; "Kingdom"; States" 
For example:
the Dominican Republic, the United Kingdom, the United States