Where's the moats?

This may have been covered before but I just realised that there are no moats in this game...I assumed MTW1 would not have had them for implementation difficulties but MTW2...?

Ive also been reading up on classical period warfare, where moats (or at least- large trenches) were used to disrupt enemy seige operations dating to well before the medieval period also...

What gives?

I've seen things resembling moats surrounding some of the forts in the Britannia campaign. Water surrounds most of the stone fort, making it only possible to approach near the front gate.

Problem is, the water doesn't go all the way up to the walls, which leaves enough room for ladders and even siege towers to approach the gate, then turn left or right and deploy against the walls to the side.