If you aren't beating the market you're losing money in opportunity cost, because you could've just bought an index fund and made more.
(Also, you don't just need to beat pure chance, because pure chance is not guaranteed — or I think likely — to result in net zero losses on average, since you are then in an information-asymmetric environment where your trading partner looks at data and you do not. But regardless, even if you "make" money but underperform the market, you are effectively losing money in opportunity cost!)
