Why do I do this? It may sound odd, but I've often wondered what it would be like trying to explain mountain biking to a visiting alien race. We spend ridiculous amounts of money engineering these mechanical contraptions which we then power with our own bodies over the most improbable terrain possible at significant risk of bodily injury, expending ridiculous amounts of energy only to end up right where we started (if we're lucky!). What part of that makes any sense?
On the sane side of this argument, I can burn up to 1000 calories per hour, which is very helpful to a guy who sits at a desk all day writing code. Speaking of work, I can't count how many times I've solved a nagging problem or design challenge while I was out on a ride with my heart rate pegged at 3 beats per second. More bloodflow equals more good ideas, I suppose. It's also wicked fun, a challenging and efficient way to explore nature, and beats the smell of a sweaty gym in a multitude of ways.
Strapping a GoPro to my chest, you can get a view fairly close to what I see when I ride. I've filmed a few of my favorite trails so I can watch them on rainy days: the Skills Trail in White Clay Creek State Park, and the Florence Flow Trail in Stowe, VT (which is well worth the 8+ hour drive to visit).
So, to sum up, mountain bikes are a fun and exciting human invention, and any visiting aliens would definitely leave with a bike rack attached to the back of their ship.
What the heck is "gravel biking"??? Good question, and one that the bike industry hasn't completely answered. In short though, It's a road bike with about 1/4 mountain bike DNA - wider tires on tubeless rims, hydraulic disc brakes, lower gearing, wider bars and a slacker frame geometry - meant to cover a wide range of paved and unpaved surfaces. It's riding a bike that looks (and can be ridden) like a road bike, but is sturdy enough to venture off pavement onto gravel and dirt roads, and even onto some mountain bike singletrack as long as it isn't too rough.
I'd been doing longer rides that linked multiple parks using sections of road. When the dirt trails are too muddy, there's plenty of "all-weather" gravel roads and paved paths nearby to ride, and endless new combinations of routes to connect them. I'd already started doing this on my mountain bike, but riding big expensive knobby mountain bike tires on the road isn't that fun. I also needed a bike that's more appropriate for charity rides and events like the Gravel Grape Crusher, which sounded like (and was) a lot of fun. I'd never owned a road bike, or any bike with drop bars because they seemed so fragile and single-purpose, but the more I looked into these gravel steeds, the more they seemed like they'd fit my needs. I got a great deal on a Niner RLT ("Road Less Traveled") demo bike which satisfied my bike snobbery without going over budget. Someday, I hope to load it with racks and camping gear to go bikepacking (backpacking by bicycle).
I track my rides with Strava, which lets me race each section of trail against my previous rides, or other riders. I find it to be a really helpful tool to find new routes or route combinations that I hadn't though of by following the rides of others.