The private timberlands, even those within National Forest boundaries, are neither owned by or leased from the U.S. gov't. They were practically given away to timber companies a bit over a century ago. Although we used to be able to travel through and collect on those private lands, the timber companies now lock them up - probably for the same reason the forest service has plowed up many of the old roads: it costs less when you don't have to constantly patrol, and certainly less than the cost of putting out fires caused by carelessness and vehicles (we had dozens of fires locally this summer just from badly working catalytic converters - one just down the road from here), repair damage, maintain roads, etc.
There are also many more people using the forests these days, and that means more folks who trash those lands, act carelessly or are downright vandalous, even if folks like you and me are good stewards and leave things as good or better than we found them. I've seen damage that may take centuries to heal - scars that still haven't healed since somebody first tore up the place over 50 years ago, and similar damage being done every summer. And while the number of people using the forests has exploded, the budgets for patroling and maintenance have been repeatedly slashed over the past 30 years - even fire suppression budgets haven't kept up with costs and regularly go way over budget, which means the money has to come from other programs like prevention, maintenance and patrolling/enforcement. Timber company's budgets are also much tighter, as they are dealing with cheap imports from Russia, disease and increased costs, too. I just don't see either private, state or federal restoring access unless they once again find a way to restore patrolling - I have zero faith in the general public suddenly developing good behavior. As a former private timberland owner who has dealt with the agencies - genuinely fine people who are trying their best and would like to keep things open, but are playing whack-a-mole with too few personel to come close to keeping up with vandals and negligent visitors - I know something about the problem - and for similar reasons we put up gates and locks, too. Most rockhounds are good visitors, but among the minority are some who are destructive as all get-out (killing trees by undercutting roots, not refilling holes, illegally hauling in a backhoe and ripping out most of a deposit, dumping garbage and human waste, ripping down or shooting up signs, digging in roads or tumbling boulders down on them, tearing up meadows and eroding hillsides - seen it all).
