It's true that Monero miners would benefit from cheaper electricity. I think more than anything it has to do with the power efficiency. A big warehouse full of CPUs would not be any more efficient than Uncle Bob mining on his gaming PC in his bedroom.

As for the noise level, I don't think cooling a million CPUs would be any quieter than cooling ASIC chips. I think it's mainly the fact that it's so distributed.

Uncle Bob might have one or two computers mining in his bedroom, which put off a little bit of noise, but nothing horrible. Where these companies have racks and racks of ASIC chips all in the same place, amplifying the noise upon each other.