The issue for hockey is players got faster AND bigger. You are right that average weight has dropped from the peak of 206 in 2005 to 201 today But in the 70's i

The issue for hockey is players got faster AND bigger. You are right that average weight has dropped from the peak of 206 in 2005 to 201 today But in the 70's it was as low as 183. The slowest 200+ pound skater today would probably be in the top 20% of skaters back then. Larger players also lead to more shoulder to head hits, just because of size disparity (see: Crosby, Kariya). The other thing that is hard to capture statistically, is that teams used to have big guys that rarely would see much ice time. Now you have many legit skilled players at 220+ pounds who are regulars.