I haven't yet found a detailed explanation of why this particular algorithm should be selected
Valid point. Magic numbers always look suspiciously.
The special commodity or medium that we call money has a long and interesting history. And since we are so dependent on our use of it and so much controlled and motivated by the wish to have more of it or not to lose what we have we may become irrational in thinking about it and fail to be able to reason about it like a bout a technology, such as a radio, to be used more or less efficiently.
MAYBE SATOSHI IS A BANANA

Maybe your mom:
http://topinfopost.com/2014/03/20/bitcoin-the-digital-currency-invented-by-thomas-edison