How come Modoc is being taken most of time?
Modoc is in the middle of TC part of map, and from all smaller team towns (You need only 3 Players in zone to keep timer running) has in my opinion best PvP map, that allows all type of fighter compositions to perform well against any other compositions, plus there is no blind spots or bugged map scrolling when you play on higher resolution.
It seems like it's the most popular town. Other towns are barely ever being taken.
That is simply not true. With Town Control problem is that if there is no enemies to fight with, you need to spend between 1-1,5 hour standing in those towns to keep timer, and this process is boring because You can get attacked any time, ergo you need to stay focused on environment and, after taking 1-3 towns with no PvP many teams just leave rest of towns waiting for other teams to start timer in towns they already took.
This being said. Teams (not only SW, but well i will not argue on this) are taking modoc because of its location, and good map. They get bored after 2 towns, they go to do something else. Then another team gets online and starts from modoc, making this town as you said most popular town for TC PvP.
Peace.