Campagnolo Large Flange Pista (track) hubs
You can run a fixed cog or a single-cog BMX-style freewheel easily on a track (pista) hub, but the wheel dish is way too far out on the drive side to fit a 5 or greater freewheel cassette. 

In other words there is simply just not enough room between the hub flange and the frame to support a wider cassette. Modern multi-speed hubs have the spoke flange set in further towards the center on the drive side. Track hubs do not.