what are the practical advantages of using radiator coolant over plain or distilled water? will using ordinary water easily destroy today's engines?

I remember when I was still a kid (sigh) and we still had our tough Ford Fiera (the first AUV?), everytime we cross the stream before climbing a steep uphill to our farm, my father will just fill a bucket of water from the stream and pour it directly to the radiator...no overheating going up

now pre-packaged commercial coolant is everywhere which we all know is not too environmentally friendly.