I'd have to guess that it's a more profitable market. I'd assume far more people are likely to be persuaded to try their hand trading since they can make a million dollars in only a couple weeks with little risk and only $1000 down! A lot of shops have introducing broker or similar programs where you sign-up clients for them and get a cut of the spread for every trade or commission or similar. Has the benefit of not being illegal, and, free money!