Actually, there are two answers to this question, a long one and what you can read above. I'd like to summarise the long answer. Briefly, if you compare the number of players online with the number of settlements, you come to a ratio of 3:1 to 2:1. We all know the old saying, the more, the merrier. So, the more players are at one place, the more will join (unless they do naughty things).
But also, when you take a more qualitative approach, the more differences between characters, the more interesting roleplay becomes. There is a halfling town for halflings. They can meet there to talk about cakes. Hooray. How interesting. But when these halflings now get in contact with orcs, humans or even magicians, interesting adventures can be plotted. Not about cakes.
So, basically, people gather at places where there are other, different characters. But also, and now we come to Troll's Bane, they gather where there is what they need. In Troll's Bane, you have depots, NPC traders, even some quest NPCs. What do you have at Zzyathis? And what goods can you trade with NPCs of the Northmark? So, people come to where the action is and that is Troll's Bane. And when you combine all this, you can imagine that Troll's Bane will always have problems to have a unique profile beyond "The town where everyone is".
One might call this a misconception of Illarion. But in the end, the events and history of this game are carved by the players over years, so our characters have to face the situation as it is.
PS: The name of the town was, is and will be
Troll's Bane 
! You should know that...