Originally Posted by
Ra-El
Kryptonians have powers in almost every situation, except under red sunlight, their homeworld orbiting a red star is not a coincidence. Their star was turned red to ensure kryptonians would not have powers under normal circumstances.
Eons ago Krypton launched a conquest campaign and conquered almost all known universe, until a group o rebel kryptonians helped stop it. Then, along with the New Gods and the Guardians, they decided to erase most records about the Kryptonian Empire and in time even the ruling council forgot about it. To ensure another conquering campaign wouldn't happen they banished space travel and turned Krypton's sun red, the only way of blocking their powers.