Why not? Because the evidence against that is overwhelming.
Are you arguing that it would be more powerful for God to create the universe as it is to make it look like it is billions of years old, rather than for God to will existence into being and have it evolve and unfold according to his plan?
What purpose would God have in trying to trick us into believing the universe only looks like it was created billions of years ago? Whereas the purpose of God breathing existence into being and it unfolding exactly as he planned reveals his majesty and glory and serves as a test.
See Romans 1:18-23