Trail running has grown rapidly in popularity recently, making the sport accessible to even the most casual of runners, but it can still be intimidating if you've never ventured off-road. If you still need some convincing to leave the comfort of your regular road route, here are just a few reasons so many runners are abandoning the asphalt.
Obviously running is a high-impact sport. Modern running shoes do a lot to help your body absorb the shock of constant pounding on pavement, but your body is still taking on a lot of stress. Since the ground has some give to it, the force generated by each footfall is lessened. Joint pain, shin splints, and plenty of other impact-induced complaints can be alleviated by running on a softer surface.
Think about it - with the exception of the occasional hill, running on a road or sidewalk doesn't offer a lot of variation. Your body relies on muscles differently running uphill versus downhill, or on a cambered versus even surface. Since a trail is constantly changing, more muscle groups will be engaged more consistently. You'll also be using different muscles - navigating switchbacks and the uneven terrain of a trail will engage smaller, stabilizing muscles that are needed for balance and proprioception (your sense of where your body is in space).
Avoiding all those roots and rocks will keep you on your toes - literally. Trail running typically promotes shorter, quicker steps and more of a midfoot-strike, which leads to more efficient running form on the road as well.
A few hours away from the road and the exhaust fumes can't hurt!
Just accept it: especially as a beginner, you won't be as fast on the trail as you are on the road. Once you come to terms with this fact, it can be pretty gratifying to run just for the sake of running. Anyway, you'll be too preoccupied with trying not to trip to worry about how fast you're going.