The Park Service, which often competes with the Bureau of Labor Statistics as my favorite government office, states that the valley floors have always been open, with Native Americans regularly setting fire to clear trees. However, this is still land management at work, even when done by someone other than the federal government. What is happening at the NPS is short-sighted. At work is a valley floor trying to recover from thousands of years of clear cutting and man-made burns. It seems that tourist pictures are taking precedent over nature.
Truthfully, the problem at the National Parks is that the majority of visitors never actually hike anywhere in the parks. I can't find a firm number, but if you google "national parks trails 'never venture further than' ", you'll see the percentage of visitors is over 80%, and the furthest distance is less than a mile. I experienced the phenomenon at Rocky Mountain National Park at Bear Lake. Beautiful, crowded Bear Lake. Squeezing by tourists to stay on the wide trail before simply starting an ascent... and finding the trail suitable for a peaceful afternoon's walk.
To see the 5,000 foot granite rock faces above a 100 foot pine tree, the obvious solution would be to climb 100 feet. That would involve getting out of the car... and hiking.