Football clubs used to draw their stewards from those people who were keen supporters of the club (as a whole) and not just the first team. (i.e. they would be the really loyal supporters who attended all the reserve and youth team games as well as first team matches). This, however, was before the Hillsborough disaster and later concerns regarding the costs to the public purse of policing football matches.
Clubs were faced with a choice of paying massively increased bills for having an large police presence in the ground or convincing the authorities that they could operate a uniform, properly-managed security system. It is for this reason that professional football clubs now use paid security staff to serve as stewards (although there may still be some volunteer stewards assisting at the turnstiles or elsewhere in the ground).
Chris