There are serious logistical challenges to building a city in the desert. Organizers must secure permits, hire portapotty cleaners (who come every day), give out art grants, etc, and these things cost serious money. Burning Man isn't spontaneous and people have realized that for 50,000 people to live civilly with each other, there need to be some rules and a modicum of organization. (The "rules," IIRC, are mostly about adhering to the laws of federal park lands, which the playa is.)
I've been twice and old timers always say it's not like it used to be...even people who have been there only three times. But they keep going back, because not-what-it-used-to-be is still better than anything-else-that's-going-on.