Because the wooden features draw unwanted attention. When you build out of dirt, rocks and logs those anti-MTBers are less likely to call the forest service and complain. Like most government agencies the FS reacts to complainants.
Am I seeing this right? Some guys not only cut an unauthorized trail, but the trail included ladders and large jumps?
I'm pretty sure that if those who cut the trails had left out such large man-made structures, the trail might have been left alone.
Does the FS even allow those on authorized trails?
Another question you may ask.....why do you have the cross post this like crazy. We get it, you don't like the FS......
This is basically it. If the trail had been round for years, say, it would be considered a "social" trail, and be more likely to let stand. But the wood features are a red liability flag to the the Land managers. More "natural" features, like log/dirt rolls and log rides set off to the side of the trail are a lot more acceptable.
I like ladders just as much as the next guy, but this is what we gotta deal with....