Keeping your cryptocurrency in your own wallet guarantees nothing about its exchange value, though; the "price level" of cryptocurrency absolutely is set by the fraudulent practices of the exchanges even if you don't go near them yourself.
There are "fraudulent practices" in the real world exchanges - look at how LIBOR was/is rigged (https://en.wikipedia.org/wiki/Libor_scandal). And I certainly hope its "exchange value" isn't exactly the same as a government currency as that would defeat the purpose of having something different in the first place...