1) The maps are popular, and therefore belong in the popular maps server.
2) Most people who populate the popular maps servers do not want to go through the trouble of switching servers to play 20-30 minutes of that map, and then switching back.
3) Some people ( me ) do not want to play those maps with 44 people in the server.

While I can certainly agree playing those maps over and over; during a short period of time, when everyone votes for that map to be played can be annoying. Still… I'd rather play either of those maps then Assault, Italy and Aztec.

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