Re: Now ask me why ...
Newer cars certainly aren't heavier in the US. The IIHS test pitted a 2009 Malibu at between 3400 to 3500 lbs with a 1959 Bel-Air with a 6 cylinder at 3500 to 3600 lbs so it's a pretty even match. For the Cadillac matchup the older model weighs in at 4500 lbs and the newer one at 3800 lbs so the newer one is actually giving up 18% or so.
I don't see either being particularly friendly to anything outside their respective envelope but the newer ones certainly aren't more dangerous to pedestrians and such. One might even argue that the softer rounded corners present less of a hazard than the older squarish designs and that some newer designs also have better visibility so as to better detect the presence of people and animals which may be preparing to cross ahead.
Some time ago when crumple zones were just becoming a thing I had both an old 60's sedan and a newer car it was interesting to look at the insurance quotes. The line items for repairing each differed greatly and I asked if it was because parts were that much more expensive for the new model. My insurance agent said it wasn't really the individual part cost but it was that given a minor fender bender with no injuries the newer car would suffer quite substantial damage and be very costly to repair while the old tank would have little more than a scratch.