I probably would stop (not that I drive)...
I would advise OH not to stop because hes got a stunning ability to say entirely the wrong thing, looks a lot like a hobo much of the time and is autistic... but he'd stop at a safe distance and call police/ambulance etc as appropriate (actually, hed stop, jibber about, ring me and ask what i thought, then do that).
I stopped (ie, insisted driver stopped) for a loose horse in the road, no signs of owner but then it was rugged up, no way of knowing where it came from so I made a headcollar out of a dog lead and put it in the first stable I could find and left a note on the door (so if you live near ish Gloucester and found a big chestnut thing in your stable circa 1996, that was me, sorry)...
Lots of other people had driven past the poor lad who was eyeballs on stalks skittering up and down the road looking thoroughly upset and confused.
I've stopped for people having seizures, elderly people who have fallen, the only time I've suffered for it was a lady in the middle of the main road and i stupidly got too close when i went to ask her her name/address etc (to see if she was compos mentis) and she punched me in the face. Lesson very much learned there, shout from further away!
Absolutely NO one stopped to even ask if they could help when my front castor tyre came off my manual wheelchair. I sat on the pavement trying to get the bugger back on and failing as I needed a tyre iron or a flat head screwdriver and i had neither... loads of folk walked past and averted their eyes :(
OH had to go off and see if any of the shops had a screwdriver and in the time he was gone, nobody stopped, no one wanted to get involved at all for fear of who the hell knows what. Fortunately the newsagents round the corner had a big screwdriver under his counter and let it to OH and I was sorted but it was a long old wait and a horrible experience.