Ahh, good hooks all. I think maybe the original module needs to make a little more explicit the fact that everyone in town knows the Moathouse is out there and always a danger.
The problem is that the module explicitly lays out that Lareth and his bandits have been going out of their way to not draw attention to the Moathouse!
I had a recent thread on this topic, here:
http://www.enworld.org/forum/general-rpg-discussion/264844-t1-village-hommlet-why-pcs-there.html
Cheers!