I've done a good amount of hitchhiking (hundreds of rides/thousands of miles) and still do occasionally. Have also picked up hitchhikers.
Hitchhiking and picking up hitchhikers has an undeserved bad reputation. Yes it can be dangerous/unsafe (as are most things), but most hitching encounters occur without incident.
If a person wanted to harm others, there are easier and simpler way to do it instead of standing out in the elements next to roads breathing exhaust for hours while getting passed by hundreds of cars while trying to get a ride.
Drivers can evaluate hitchhikers to help decide whether or not to pick them up. The more upstanding hitchhikers are dressed more neatly and clean. They have a manageable amount of gear (maybe one pack) and not all their worldly possessions., dogs, etc. They are actively trying to solicit a ride. They are standing up, facing traffic, trying to make eye contact with you, and have their thumb out and/or a sign with a destination on it. They are standing on the edge of the road in a location where there is room for drivers to pull over, including past them if there is a lot of traffic. They are frequently looking behind them to see if anyone has stopped. When they do see someone that is stopped they hustle (jog or walk quickly) to the car.
There should be an exchange through the passenger side window when the hitchhiker reaches the car. The driver should roll down their window some, or maybe motion for the hitchhiker to open the door. This verbal exchange is a chance for both the driver and hitchhiker to evaluate each other. A chance to communicate about where each plans/wants to go and further evaluate each other based on the conversation and nonverbal clues.
Some potential red flags from the evaluation that may result in either the driver or hitchhiker potentially rejecting the shared ride include: no clear destination, dirt/odor/filth, weapons, slurred/impaired speech/behavior/cognition, alcohol/drugs, etc.
Yes hitchhikers should be evaluating potential rides/drivers and it's a red flag for a driver when they do not. I have turned down numerous rides while hitchhiking.
It seems like it is becoming harder and harder to hitchhike, but it's a positive restorative exchange to receive or offer a ride. It's a way to affirm that most people are good, kind, generous, interesting, etc.