As the NHL has adapted to include more skilled forwards, the countermeasure is more mobile defencemen who can close down their attacks. It’s rare that you see a big, immobile, stay-at-home players finding success in the league now, because skilled players will just go around them. It’s also difficult for small defencemen who are good skaters to defend only by keeping up with forwards, because some of those attackers can simply outmuscle them in front of the net.
There is now a premium on defencemen who are big enough to hold their ground and nimble enough to keep space limited for the opposition, and those are the types of players we see selected the highest on draft day.