It's a nice little closed-minded world you guys live in there, but it doesn't make it correct. Fact is, most land that is now closed is that way for three reasons:

1. Environmental groups using political might and money to have lands designated as Federal Wilderness.
2. Environmental groups using legal maneuvering (threats of lawsuits and judicial decrees) as a way of forcing land managers to abandon their charter to manage lands for all citizens, and to eliminate their responsibility to allow motorized recreational access for those citizens who desire it.
3. Land managers who are sympathetic to environmental interests using motorized and mechanized recreation as a convenient excuse to limit access to only those interested in, capable of, or willing to go in on foot. This, despite the fact that foot-borne trail proliferation and staging for hikers results in precisely the same sort of damage to otherwise pristine areas.