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.
"I think it has done more to emancipate women than anything else in the world. It gives women a feeling of freedom and self-reliance. I stand and rejoice every time I see a woman ride by on a wheel...the picture of free, untrammeled womanhood." Susan B Anthony