It's obviously not from a recent source, so I wonder how old the data hails from. For example, check out the southern end of Mt Nebo
When I was hiking along that ridgeline I couldn't even tell the trail at one time followed an old dirt road. I can't even make it out on the higher slopes in the satellite photographs!
There's a similar one for Mt Timponogos, although since it is labeled Mt Timpanogos Trail, maybe the mapmakers were just confused?
Oddly enough, even with these roads included, Google maps doesn't show the old (and still very prominent) dirt road up to the reservoir in White Pine Canyon.
One reason I wonder is due to the ongoing fight in Utah regarding what is still a 'road' and how that affects Wilderness Area status of land.