So parents don't do some time in the mental hospital.
Why do children need to take naps?
Your sanity.
Same reason *sigh* geezers need to take naps.
Young children need more sleep than an adult. There little bodies are growing and rest gives it time to rejuvenate. Their bodies get on over load and they become cranky if they don't get the rest they need.
Very young children do,.. Older children, maybe not so much