Because the simple maps were easier for players. All of the maps were basically flat one level terrain. At the time, it was new and exciting, but now the levels lack depth. Most people don't play it anymore, so their memories are better than reality. I still go play it because I bought the digital version on XBL, and it is ok, but the maps are one dimensional.
Game Devs...you will never please all of these complainers...so just ignore them and keep giving the rest of us the games we like.