The majority of Egyptians live along the Nile River and Nile Delta because

It was the most fertile part of Egypt.

Explanation:

The Nile River is the most important and striking feature of Egypt, without it life would be almost impossible in this area. People have been fascinated since the early days by the fact that the Nile flows about 7,000 km through the desert, and at the same time delivers vast quantities of water necessary for life. Unlike the Euphrates and Tigris, the Nile is a very reliable river, which flooded its banks at a time when it is most suitable for agricultural activities - it floods in June and the water recedes during October. During this flood period, the Nile leaves behind a rich layer of fertile black soil at the right time for winter sowing of cereals. The Nile provided the Egyptians with a great opportunity for communication and transportation. The river flows northwards and ensures ease of navigation in this direction, while at the same time the main winds blow southwards, which provides ships with the possibility of counter-current navigation. It is no wonder, then, that the name of the gift of the Nile is added to ancient Egypt, as Herodotus mentioned it.