Here's why:
* Krypton's Red Sun: Krypton's sun is red, which does not have the same energy output as Earth's yellow sun.
* Kryptonian Physiology: Kryptonians are naturally strong and have advanced technology, but their abilities are limited.
* Earth's Yellow Sun: When exposed to Earth's yellow sun, Kryptonians absorb its energy, which grants them super strength, flight, heat vision, and other powers.
So, while Superman was a normal Kryptonian child on his home planet, he developed his powers only after being exposed to Earth's sun.