Do they though? At the end of the day, the guy/woman that owns the majority of shares has the final say. As a club, we don't currently need a supporters trust. That's not to say in the future there might be a case for it.
What purpose would they serve? Might have been appropriate back in 1996 but don't really see the point now. We've got a fan at the helm so the only need could possibly be if he ever chose to sell up.