The other "useful" think that a stockpile of illegal goods can be used for, is BGS work. Selling stolen goods to a black market slightly decreases the influence of the faction that owns the black market. Its one of the few guaranteed ways to create negative influence on demand that doesn't involve massacring innocent NPCs.
But since carrying around a stockpile of illegal cargo is generally inconvenient, both in terms of unwanted police attention and in terms of taking up valuable storage space that could be put to better use, it's generally only something a fleet-carrier-owner can afford to indulge in.