I have noticed several posts lately and have experienced the dilemma myself several times of encountering closed Forest Service gates. A well planned expedition to activaate a summit can be ruined by an inconviently and unexpected closed gate.
Most of my summits here in Montana are accessed first by travelling for considerable miles along Forest Service roads to get me to either a trailhead, scramble, or to the summit itself in the case of a drive-to summit. I had other passengers along the other day to activate what looked like an easy drive-to lookout. Three miles before the summit I encountered a newly placed gate restricting the travels of any motor driven vehicle. My passengers were in no shape to hike the distance and did not want to be left alone in the truck for a few hours so the activation was aborted. And there have been times when by myself that the added miles of walking the extra distance meant that returnng from the activation would have been in the dark or I was not able to walk/hike/scramble that many miles.
I took the advice of K7VK Vick Applegate and have started taking an old beater mountain bicycle with wide tires in the back of my truck when there is the the possibility of encountering gates. I just park the truck and hop on the bike and pedal the remaining distance. Granted, there are uphill grades that are too steep for me and I end up walking the bike for some stretches, but I get to the trailhead. The best part is coming back downhill as it's fast and fun.
You need to make sure it's legal to do this however, as some gates are posted "Private Property". For the most part in my experience, the restriction is for motor driven vehicles to reduce the environmental impact.