I have been both a hitchhiker and a ride provider...
Have gone from New York to San Diego, and New York to Florida both round trips. Got One Ride from Long Island to Panama City, Florida - best hitch I ever got - the Driver had to get to south Florida, and was willing to let me drive while he slept - when I offered fuel money, he countered with basically "door to door" service -took him out of his way about three hundred or four hundred miles.
All the hitching I did while in College, some thirty years ago.
I have offered rides at about a constant rate - about two rides a year. I will accept someone who is in obvious distress, standing by their broken car, in the desolate stretches, or in inclement weather. I will not accept a rider who is unclean, unless they are also injured. I never take money, nor ask for it - I just tell them to "pass it on" when and if they are able, to someone who needs help. If they start to light up without asking, I stop and put them out. If they ask, i offer thm the choice not to smoke, or to get out.
The only time I take multiple riders is if they were in a wreck, or are by their damaged/disabled car, and look like a family.
Just like a lottery, you can't get killed by hitchhikers if you don't pick them up, but i have never had any problem with any I have picked up.