Most of people who got scammed lost their BTC on shady exchanges, how's OS relevant in this case?
This. I'd imagine most people who were "robbed" had bitcoins stolen from dishonest exchanges or online wallets. And I'd imagine the next most common source of thievery was people who downloaded malware designed to sst or perhaps because they down, used weak brainwallets, or other forms of human error. None of which I'd really blame on the OS.