What is so special about visible light spectrum?
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It’s only a hypothesis, but the visible spectrum is the only light that is given off by the sun in large amounts, reaches the surface, and easily passes through water (which is where vision evolved), so it’s kind of the only game in town.
By the time life moved onto land, vision was highly specialized. Ultraviolet and infrared can be used on lands since they pass through the air, but it’s tough to get there via natural selection. Marginally functional UV and IR sensing eye cells would dilute the already working other ones and likely make the organism less fit since it’s vision would overall be worse. It’s kind of like trying to evolve another joint in your limb. No matter how good it might be in 10 million years, it’s almost certainly bad NOW and will be selected against.
All that’s before getting into the problems of damaging other vision receptors if the eye lets in UV and noise issues since the animal’s body is a source of IR. Not that some animals haven’t come to use it. Some insects can see UV, and some can sense IR but don’t use their eyes for it.
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