Probably because on your way to the Mojave you have to stop at the Mad Greek restaurant in baker and get a gyro, but you cant do it going to Joshua Tree. (I tend to use restaurants and other little dives as landmarks wherever I go.)
Its getting a little late in the year for my taste though. I sort of prefer to be in and out of that area by March.
We were in Death Valley a year or so ago and I decided that the next time I go Ill bring a couple of cartons of cigarettes with me. I overheard quite a few people asking a ranger if there was anywhere close by where they could get cigarettes. To one man she replied honey, theres nothing close by. Ha. Course its probably illegal to smoke in a national park or preserve now