Meeting Halls were introduced to allow players a location to meet without fear of Portal Storms. Both the entrance and exit portals are tiable and summonable. Not all towns have halls.
Prior to the introduction of Housing, Meeting Halls were more popular locations for Allegiances to congregate in. Bind Stones are found beside the entrance to each hall allowing monarchs and officers of rank 3 to set town recall points.
Meeting Halls are one of the few locations where privies are found.
The Meeting Halls also provide a pool which restored Mana, back in the early days of AC a popular place for young mages to do their spell research:
You feel tingly as the refreshing waters wash over you, restoring 6 points of mana.