From what I've read, and otherwise gathered from talking to folks that don't ride, motorcycles scare the hell out of a lot of people. As in, "Oh my god, that motorcycle parked over there is going to lunge at me and eat my travel-sized dog."
People have told me they don't ride because it's too scary, and they don't know how I do it.
Here's something to consider: motorcycles scare the hell out of people that do ride, on occasion. Any biker will be able to tell you about a time he/she almost shat in his/her gear. It might have been an oncoming truck intruding in the lane, or gravel in the middle a fast curve. If you've never had to check your pants after a ride, you haven't been riding for very long.
It's not a lack of fear that lets us continue to enjoy riding, it's just a good supply of nerve. Nerve as in ability to cope in a demanding situation, in equal measure with impudence and audacity.
Some people don't have enough nerve to get on a bike in the first place. Some don't have enough nerve to make it beyond the first high-intensity experience. That's OK. At least they know their limits now.
But a select few are the sort who survive a close call, yell "Wahoo!" and ride on, because letting fear win is unthinkable.
Long time riders are the ones who have it together enough to face a terrifying situation, respond correctly, and then look over at fear and death and give them a cheery wave just to shine 'em on a bit. It takes a lot of nerve to get back on a bike after that.