Why is it impossible for camera sensors to function the way the human eye can? What I mean is, why does a certain portion of the image have to be over/underexposed if we compensate for dark and light areas respectively when taking a photo and deciding on the aperture and shutter speed settings.

I understand that the light getting in depends on aperture and shutter speed but since DSLRs are digital, can't there be a technology that would enable each sensor cell use of its own metering and therefore they wouldn't all be subjected to the same amount of light but depending on the metering, a CPU of the camera would shut off certain cells as not to overexpose them.

I hope I'm not saying nonsense. It sure seems to me like a plausible idea.