First, in a situation like that, I'd think legally you should pull over safely and park and then deal with the situation. I don't think you want to create an even greater danger --- in your case, someone rear-ending you and injuring or killing you and the child (just an example).
Second, cars let you do all kinds of illegal things, just because it lets you doesn't mean it's legal.
It's just like how driving a manual transmission and coasting in neutral (clutch disengaged) is illegal in some states. People still do it.