I'm not an expert (this is not my industry, so please correct me if I'm wrong) but I imagine it has to do something with the initial cost of entering the positi

I'm not an expert (this is not my industry, so please correct me if I'm wrong) but I imagine it has to do something with the initial cost of entering the position. With a futures position you may end up losing more than you put in (your initial margin) but assuming you went long a stock without using margin, the most you could lose would be your initial investment. But perhaps it's not a fair comparison. I would say that buying 100K of stocks on margin is similar in risk to having a futures contract with a similar value, all other things equal. Also, with forwards (not exchange traded) there would be counterparty risk if no clearing house was involved.