They are all just scams of trying to be the one guy who manages to screw a different guy over for profit. Its the same as the Stock Market Sharks who destroy entire companies for a quick buck, but this time the barrier for entry is low enough that regular guys can get in on it.

As you said, its all worthless until you can use them as currency like a Dollar, which leaves mostly just Bitcoin as anything but scams for chumps. And no one in these circles seems to be interested in "legitimizing" them in that way either.