Most of the big trees in HCTFs were left by the old Timers for various reasons, but mostly because, like Reg said, they were too much of a bother at the the time.
Now there's a lot of big trees around these parts standing because their grace and grandeur enamored someone at the time to 'not cut them.' The Slater tree in Sonoma County is one. A really big one. The Henry Tree in Greenwood Creek is a real beauty. Then there's the McCabe Tree in Gualala, a fatty. The Standish Tree in Leggett is a whopper, and that one has an undercut in it. A close shave! Don't forget the Coombs Tree. Oh, there's bunches more, and because they're all beauties I climbed most of them a long time ago.
Nearly all the big lone standing trees here are named in honor of the people who either saved them, or as a memorial to someone that died on the job.
A couple show decline, but most are doing quite well. But that's redwood. If they were fir or cedar they would've gone into decline from exposure a long time ago.
The stories behind those big lone standing giants are all very interesting.