I-CW's are designed to be short.  They are short enough so that people playing want more, meaning they will jump on regular FS.  It's like CG's, if it's only been running for a few maps and the server crashes, people will rejoin pretty quick 'cause they want more. However, if the server decides to go kaput about halfway through, especially after a good round, people quit because they are satisfied that they had a few good games.