yeah i want more stuff on the map, if it was any other environment other than a desert it would be almost impossible to avoid a lot of structures, pick any major city in the world or even your town, is every location a mile apart? thats not even realistic, even outside of a city, there are outlying areas with "civilization" and buildings, neighborhoods, businesses, industrial areas, factories, apartment complexes, farms, power stations, gas stations and on and on, you can't rationalize having such a barren world, new vegas isn't suppose to be like the north pole, you're defending nothing, you're saying the less the better, so when you buy a pizza do you just take one bite and say you're full, i eat like half the pizza, so yeah i think picking a desert just for a reason to not put much on the map is laziness and like president eden says, and i quote "laziness breeds stupidity".
Do me a favor.
Get Google Earth of some other photo map software and find Las Vegas. Look at the area surrounding Vegas itself. Around Sloan, Nipton, Goodsprings, Boulder City, Searchlight and the Solar Power Plant (All real places btw). The Majove really is that empty and spread out.
Sure they 'could' have built up more between now and 2077, but then there was a nulclear war and 200 years on neglect. And Fallout 3 wasn't exactly packed with stuff. There were areas of the map with nothing, but the odd rock and peice of cracked road for a good distance around.