Why was invading and capturing nubia was so important in egyption history

In the antiquity the territory at the moment called Nubia was very influenced by the culture of the Ancient Egypt, mainly during the epochs of apogee of Egypt, being a species of Egyptian virreinato.

For the ancient Kemet (Ancient Egypt), Nubia was "Tai-Seiti" (the land of the "people of the bow"), population hardly subjugated, because they knew how to use their bows and arrows.

Pharaohs of the New Kingdom, like Ramses II (1290-1224 BC), rose to royalty because they could prevail over the Nubians, drag them into defeat. To show his divinity, this sovereign decided to build his great temple at Abu Simbel. Ramses II built the temple of Aksha in the center of Nubia, and Viceroy Setau and his wife were represented, worshiping him, in the temple of Faras.

Nubia was divided into two large sectors, Wawat to the north (to the second Nile River cataract), and Kush to the south (between the second waterfall and the confluence of the Blue Nile and the White Nile). To the north was the Egyptian province Ta Seti ('Land of the Arc').

Kush was a region located along the valley of the Nile that included the south of the present Egypt and extended by the north of the present Sudan. It was rich in raw materials, especially gold, so the Egyptians very early sought to exploit these resources. Egyptian texts relate, from Pharaoh's time, Narmerlas expeditions to Nubia, but it was in the era of the Middle Kingdom of Egypt, when they conquered Lower Nubia (from the first to the second Nile waterfall). From Mentuhotep II the campaign was undertaken and from Sesostris I the conquest can be considered concluded.