Why did the Egyptian army eventually become hired?

Ancient Egypt was a very developed country, both economically and militarily. The army allowed the Egyptian pharaohs to hold the borders of their state for a long time, often expanding territories at the expense of neighboring lands. Here the organization of the army itself naturally played an important role. Over time, the Egyptian rulers decided to abandon the usual army, and instead recruit an army of mercenaries. Thus, this significantly increased the reliability of the troops in the event of uprisings.