i would have stopped, unless there were already 2-3 other cars stopped first. With no CPR/medical training there wouldn't be much i could do if other people were already there, but i would call 911 as soon as i could.
Sometimes it might not be that people have something better to do. It seems EVERYONE is afraid of getting sued. Blame the lawyers, greedy lazy bastards, juries that award lawsuits just to screw over insurance companies because "they can afford it." or who ever you want too.
If i were the first person on the scene, no doubt i would stop, but in the unfortunate case that the kid dies because I don't know CPR and just stand there while it happends, i very well may lose my shirt becausesome fucked up parent thinks, "if you don't know CPR to save my billy, why even stop"
I'm not saying it's right, it's sad on many levels, but don't solely blame a bystander for passing by in the land of "if something bad happends, sue"