Cursed Victorians. They've polluted our understanding of medieval society and culture.

As has been said before/above, a gate hinged upon the side, or sides, has a very lovely advantage to the defenders. When it is time to sally forth to reclaim the fortress, a defending force can be certain that the area immediately outside the gate will be clear, or will be cleared when the gate swings open. With the help of a few consistently placed spikes on the outward-facing gate, any aggressor unlucky enough to be too close will be taken for a very point ride. Everyone smart enough to get out of the way will push themselves back away from the gate... and into a better position for any wall-mounted defenders with projectiles.