Culture, religion, philosophy, ethics, etc.
Even assuming they had the foreknowledge on the effects of a different sun and that knowledge was widespread and deemed reliable... that doesn't mean their society would adopt it. Consider the fact that we could engage in eugenics, sterilization, and designer babies today if we wanted to. We could outlaw people with genetic defects from reproducing, we could terminate any prospectively "defective" child before being born, we could modify all humans before being born to meet certain specifications... but that's an anathema to us. Just like there is a ton we could learn from human experimentation and testing, but we don't for moral reasons.
Similarly, we have the technology to pump you full of steroids from birth or to amputate your limps and replace them with artificial ones which could supply a specific mechanical advantage... again, we don't for reasons that go beyond the inability to do so.
Perfection and strength are in the eye-of-the-beholder.
What little insight into Kryptonian culture we have, we know that they deemed their sun, Rao, a god. Shielding one's self from his light and accepting the light from artificial sources may well amount to heresy.
There's support for the idea that Kryptonians would find a super-powered society an anathema. Remember that's Zod's entire mission. To replicate and recreate Krypton exactly as it existed before with the sole modification of himself as leader. So did his plans include dropping all his men onto Earth so that they could ALL have super-powers? Clearly not! Zod went through every effort to put as few Kryptonians on Earth as possible. He had every intention of creating a New Krypton where none of them would have powers. Why was he (and Faora and Nam-Ek) an exception? That's the role of a soldier! Killing is an anathema! However, the soldier is given limited authority and window to do so within the scope of war. Here, Zod gave himself permission to have super-powers... only to be discarded as soon as Krypton was rebuilt.