Its written in the Advanced map making tutorial at the wiki:
I integrated traps in the new maps i made, but if these would stay the only one with traps it would be a bit...sad.36. Traps are really necessary![...]
I had the idea of picking randomly maps from the worldmap and edit them with some more or less mean traps.
What do you think of this idea in general? If you like it i may post the edited maps in the developers section to don't spoil the new traps :p.