I agree that the amount of land a 7,000+ wooden coaster takes up is a big factor in why more parks have not built one. Son of Beast is a lot more compact than The Beast, but still covers at least 12 acres of ground. For some parks 12 acres is hard to come by, and would be used for more than one coaster or attraction.
Second I believe the Beast is not only the longest wooden coaster, but the coaster that covers the most acreage at 35 acres.