Not to wade into the brewing controversy here, but I ride singletrack, because we have gorgous singletrack. I also avoid fire roads (as much as possible) though there are some that people have turned into trails (goddess bless them). And I live in AZ, also wildfire country for whatever that's worth.
I'm going to agree with everything Martian Destiny said and add...
I ride for the adrenaline and the rush. If I want scenery I'll hike, if I want fitness I run. If I want thrills I mountain bike, and there is a big thrill to be gained biking UP a seemingly impossible climb, and cleaning it. Then you get to go down, double the fun.