Computing the truth takes valuable resources, such as time and energy; this can favor the evolution of heuristics that cut corners on truth and resources. The desire for social acceptance can lead one to adopt false beliefs as a form of virtue signaling. Strategic lies can be advantageous; the best liars are those who are not aware they are lying.
A useful metaphor is to think of our senses as providing a user interface to an unknown reality, much like the desktop interface on a laptop. The icons on the desktop let you control voltages in circuits of the laptop without you having to know anything about these circuits. If you ha to toggle voltages to craft an email, no one would hear from you. Knowing the truth will not make you more fit; it will make you extinct. Evolution shaped your senses to guide adaptive action, not to know the truth.