I'm having a tough time finding reliable statistics. One source has hiking related fatalities in the United States at 4 deaths per 100,000 hikers (estimated 57,000,000 hikers) with about 11,000 serious injuries per year. Automobile accidents in the United States kill 12.9 out of 100,000 people (not drivers) each year. We have about 330,000,000 people in the United States, so someone who is more mathematically inclined can feel free to figure out how much more dangerous hiking is than driving.
Very often the only alternative I have to hiking solo is to not hike at all. While there are inherent risks to hiking, I don't really think of it as an overly dangerous activity. While I take reasonable precautions, I recognize there's always a chance I might run into some unexpected difficulties with potentially dire consequences. For example just last summer I went for a walk during the heat of the day and forgot my hat. I made it about 3/4ths of the way through my normal route before cutting it short and heading home because the sun was beating down on my more than I expected.
I would agree that it's better to hike with another person both for safety and just because it's more fun. But generally speaking, hiking isn't a super hazardous activity. Now if you'll excuse me, I'm going to dive 4,000 meters underwater in this submersible I made with a window rated for 1,300 meters.