First of all: there are even people who say "please have all Nexuiz maps in". I can definetely say "no" to them as quite some maps don't fit the 1on1 style, size, item placement or whatever. If they were (all) in, the matches would either become boring (because it's too big) or rather one-sided because of bad item placement, etc.
nexdm02: it's simply it's size that keeps me away from putting this map into the mappool. The map is best played at 2on2 or 3on3 max. Item placement would be quite good for 1on1, too, but it's just too big for it
nexdm04: this map is unsuitable for 1on1's because it is too open. The player who got the nexgun will do 80 frags in a row, leaving you with a 80:0 result after 15 minutes (blame the pillars

nexdm06: This map has horrible performance and all the important items are very close to each other, just to name the MH, RL and Nexgun. A player who controls that area will easily dominate the map.
nexdm08: The itemplacing here is horrible as well. Two MH's directly next to each other, as well as the mortar and Electro. Mapcontrol won't be lost that fast if a player is well equipped.
nexdm11: Beside the fact that this map is sloppy, doesn't have too good performance and will make you clip at every f*cking corner the map would be fine, but also item placement isn't too good and it's buggy in 1.5 (mortar is missing).
nexdm12: It's the same like for nexdm04, the map is too open, mapcontrol can be maintained for a very long time
nexdm13: that map is a bad joke, sorry (too open, horrible performance, ....)
nexdm15: tooooooooooo big (way too big, really). Item placement would be fine .. for 2on2 and greater perhaps

nexdm16/17: look at nexdm15