The answer is that God wanted the Egyptians hooked into thinking that they could match Moses and Aaron step-for-step, so that later - when Moses and Aaron would perform greater miracles - the expert Egyptians would fully appreciate God's enormous powers.
And that's exactly what happens. After the third plague of lice, Pharaoh calls in his magicians to duplicate what Moses and Aaron had done. But they are unable to do so. At which point the magicians turn to Pharaoh, acknowledge God's awesome, infinite, power, and declare, "It is the finger of God."
The Talmud explains that the lice were too small for Pharaoh's magicians to manipulate. In a way, that's similar to our world today. Science produces so many magnificent wonders - atomic energy, space flight, genetic engineering. Yet it's all predicated on using existing energy and resources. So where did all that original matter come from?!
That's where God comes in. To create something out of nothing - the miniscule building-blocks of life - that is something of which only God is, was and will ever be capable. The encounter between Aaron and Pharaoh teaches us not to lose that perspective.
Moses, the great leader of the Jewish people, went so far to show appreciation that when God asked him to hit the Nile river with his staff in order to signal the beginning of one of the ten plagues, Moses objected and asked that his brother Aaron do it instead.
Moses felt grateful to the river, which had helped save his life when his mother had floated him on a basket to escape from Pharaoh. He didn't even want to hit an inanimate object to which he felt grateful!
We can learn from here the Torah value of trying to recognize even the smallest good that others do for us.
Let people know that we recognize and appreciate the good things they have done for us. It makes them feel good about themselves, and encourages them to do more good in the future.
""Moshe (Moses) spoke thus (that the Almighty will take you out, rescue you, redeem you with great judgments, take you for a people, be a God to you and bring you into the land of Israel) to the Children of Israel and they did not listen to Moshe because of anguish of spirit and hard work." (Exodus 6:9)"
Rabbi Meir Simcha HaCohen, in his commentary Meshech Chochmah, explains that they did not listen to the message that Moshe gave them because when someone is suffering very much, all he wants to hear is that his suffering will be removed. He is not yet ready to hear that he will have good fortune and much success in the future.
Parshat Va'eira tells about Aaron performing miracles in front of Pharaoh, and how he turns a stick into a snake.
So what's Pharaoh's response? "Big deal!" he says. "Egypt is full of magicians!" At which point Pharaoh calls in his young children who proceeds to also turn sticks into snakes!
Now, God certainly knew of Egypt's advanced knowledge of magic. So why did God have Aaron perform feats that could be so easily replicated?