If your standard for a minmaxed cargo Cutter is a shieldless paperplane that can carry 750 something tons, then by the same standard gankers cannot and don't fly minmaxed combat ships. That would be a ringfighter FDL with c1 fuel tank, 2D FSD with SCBs and HRPs in every single optional slot.
Gankers' ships, on the other hand, need to be able to jump so they need to carry the dead weight of extra fuel and a heavy FSD, which will make them slower. They also need an interdictor if they want to catch you, which means weaker than minmaxed hull. If they want to follow your high wake, they'll need a wake scanner as well which means one less skill booster (weaker than minmaxed shields in other words). If they want to be able to kill ships that have strong shields, they'll need to sacrifice one hardpoint for a Grom missile launcher (which is a pretty crappy weapon otherwise). Pirates need other modules as well, such as a cargo rack, a manifest scanner or a hatch breaker limpet controller.
All the above make pirate and ganker ships worse than minmaxed combat builds.