it is because how the market capitalization is being calculated.
Market Cap. = Supply * Price
when you don't have one of these variables you can not have the Market Cap either and these coins do not have a clear supply.
i am not familiar with these to tell you why but i remember they didn't have M.C. for BTG because it wasn't started yet to mine and also because back then they had to do a premine of 200,000 BTG so it was not clear how much the supply of it should have been.
as soon as it became clear, they filled in the variables and BTG had a market cap.