It's quite obvious that hutts are gangsters, so that would include anything like slaving, spice dealing, smuggling etc. However, in order to subdue someone into slavery to begin with it would require some sort of strength over the other species. In order to become some kind of drug dealer it requires some brawn or physical ability to begin with, to gain a position of power over your peers. Even if you don't actually appear that strong you still need to be intimidating in some way. And the way hutts are perceived is that they are some fat slobbish worms that can barely move. Sure they could pay people to smuggle/slave trade for them, but they require some kind of ability to make the money. Unless they some how poop gold there's really no reason they even got their money or power to begin with
