I work backshop at a very busy course so pretty much see every bag that comes through on the way in or way out and they are extremely rare, like maybe have seen one set all season.
I do see a few people ditching the 4 iron, sometimes the 5i as well. Most of the marshals and starters i play with are geezers ( 65+) and typically only carry 6 iron down. If they design helps elevate the ball and us easier to hit then do whatever it takes.
I still carry and use a 4iron, but depending on the course also have a 4hy I can sub in if I need a higher softer landing shot versus the 4i. Different trajectories but they end up about same distance