Why "PORK" is Haraam in Islam?

FOODS:

Several  food comapnies are offered halal processed foods and products,including halal like spring rolls,chicken nuggets,pizza,burger etc..

 Halal ready meals are growing consumer markets for muslims in britain and america.

IN THE QURAN: 

The words halal and haram used in Quran to designate the categories of lawful or allowed and unlawful or forbidden.

The most common examples of haram(non-halal) food is "pork".

The quran forbids it in Surah 2:173 and 16:115.