You can trade cryptocurrency for fiat or vice versa in a peer-to-peer manner for some of the exchanges you listed. Meaning, you can simply meet up in person and pay/receive cash. This is great for people without PayPal or bank accounts and if you want to be more anonymous.
Ok, so what I gather from everyone's responses is the benefit of being anonymous. Because it's clear that it's not cheaper and is not necessarily faster unless you're physically meeting a stranger.