I hate to point out the obvious. But having a thieves guild in a town, even a town started by reformed pirates, is one of those fantasy things that is really dumb to me.

I know you aren't supposed to think about these things. But why would you make a guild basically saying "We're a bunch of organised criminals. Local police please raid us if anything goes missing from anywhere." So they have to be either shadow organisations or relentlessly mocked like in Discworld.

FFXIV sidesteps this by making the Rogues guild espionage task force and giving them a strict code to enforce.