For one thing, ALL the Tour Pros hit an iron the way it supposed to be....hands ahead of the ball at impact resulting in a descending blow which takes loft off the iron. It is also a fact that the AVERAGE tour player's clubhead speed is substantially higher than it was back in the Nicklaus/Miller era on tour. Back then the average driver speed was about 104-105 with avg 5-iron speed around 79-80 while today we're seeing that average be around +9 to +10 mph higher....because of stronger, more physically fit golfers.
Most of the tour players do not use irons based on a 24, 25, 26 deg 5-iron loft - they use iron lofts more in the area of a 27-28 deg 5-iron. Now granted, back in the Nicklaus/Miller era, irons were made more based on a 30*-32* 5-iron and it was more common to see the avg tour player hit 7 iron from 150, with big hitters using 8 iron from 150 - but still when you see the avg clubhead speed be that much higher today, this is a chief reason you see the 175 yd 7 iron and 200 yd 5-iron with a slight loft decrease contributing a little.