But you're talking about cryptocurrency exchanges like Poloniex which tend to be centralized either completely or to an extent. So, of course, these websites, these platforms, as middle men, can do things like that, similar to what central banks do with fractional reserving. You said that many people prefer the simplest things and I agree. So, people tend to prefer those exchange websites, etc, and I think that is what you said. I agree. It can be harder for people to take care of their Bitcoin private keys themselves, to have their own wallets. But my main point was in regards to cryptography itself as people can conflate between the exchange websites and the actual cryptocurrencies themselves.
RE: Warning: How Bitcoin and the Cryptocurrency Industry could be Defeated: Fractional Reserve Bitcoin