If we changed them, they would be 4 three month long seasons. Newer mappers probably won't have as long an attention span as some better mappers. It's not all "I have to release an amazing map!", you know. have some fun. This organization was made for 2 reasons.
1 - To make mapping more enjoyable. Everything's a bit more fun when you're competing. Sure, there's more pressure, but the competition provides a lot of time, and the ability to work in groups makes it even more enjoyable.
2 - To attract more mappers to actively join in the DP community. I'm sure a lot of people have tried to map, or have even made a playable map. They simply don't release the map to the community. Look at Elimnator (
http://dplogin.com/forums/index.php?topic=17730.0). The mapping community probably have never heard of him, but look at his maps. Sure, some of them could use some work, but a lot are playable, and his mapping skill could easily be developed.
Some people in the community think, "Why bother mapping? It's just a game anyway." I myself am not a hardcore gamer, and I understand that valid point. However, being able to map, or at least know the basics of 3D manipulation (mapping, 3D modelling, etc) can help you get a challenging yet entertaining career like a game designer. It's not all games either. Have you ever thought of mapping like arranging props in a movie set? Not only can you go into games, but if you're a great mapper, chances are anything to do with design, you'll do better at.
EDIT: Fxed the first post for clearer instructions.