Questions regarding how Superman's powers work and what role Krypton's gravity has on him rumble on eternally, writers still like to remind us that Krypton's high gravity plays a part in what he can do but never actually explain what it is that the gravity differential does for him...
But check out one of the earliest Superman Origins and actually, it all makes a neat sort of sense:
Now that's how it should be.
Nice. There's another sequence where Superman is explaining how their powers work to Supergirl. It's a Silver Age issue that I've been trying to find again with no luck, but it explains that it's the solar rays, which penetrate through the Earth, not sunlight that power them.
Gil Kane actually reversed the concept during his run where he introduced the new Brainiac. Under Kane, Superman retained his super-senses under a red sun. I was surprised and intrigued when I read that, but I never saw it used that way again.