Why so concerned about high ISO?

Seems too many of you are complaining about high ISO on these cameras. Are y'all not wanting to use tripods or flash? The D800's sensor is densely packed with pixels so there is more heat generated. It's not going to be a high iso camera. Use the d700 or d3s for that, it has bigger pixels and makes less heat. Anyway, im just trying to figure out why the high ISO is so demanding. I use flashes and low ISO. I have 8 flashes and use them like Joe McNally does, of course I am no where near as good as he is, but I assume many of you don't like to use flash. Is that why the need for high ISO comes in?
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