Because we live in a world of opportunity. There are many more hazards out there than there were when I was 16. My first car was lucky to reach 75 mph. Some of the second hand cars being provided to 16 year olds today will easily reach 150. People knew each other back then as well. My Dad would hear from his lodge buddies that I was speeding and I would lose my car for a couple of months. Today, our children are a tree in the Forest. I would use every available tool to give me the advantages that could help me shape the character of my children.
Today's cars are much safer to drive at higher speeds (and are safer at any speed) than the cars of yesterday, all jokes to the contrary. I'd have to dig out my safety council text to provide specific citation, but accidental car deaths per mile driven have decreased dramatically in the last 40-50 years.
Can't challenge the lodge buddies statement though - still think that's largely a function of where you live. My sister lives in such a "everybody knows everybody else" sort of area.