I've been thinking about this a lot these past few days, and my conclusion is that this was done with intent in order to force us into using the "Multiplayer Car" online. Why was this done? Simple. So we pay for the liveries in order to keep us intrigued. I can't think of any other reason as to why this feature isn't in the game, and chances are I'm probably wrong. But in my opinion, its more than a coincidence that we don't have one of the major features of past games the second micro DLC is added.