Butterfly wings are covered with tiny, colorful scales that help them fly. If you touch their wings, the scales can come off, and the butterfly might get hurt or have trouble flying because those scales don't grow back. So, it’s best to look at butterflies carefully without touching their wings to keep them safe and happy.
Another way to say this is: When you gently watch butterflies without touching, you help them stay strong because their wings need all their little scales to fly well. Touching their wings can take these scales away, and the butterflies can't fix their wings or fly properly anymore.