I think many light-weight on-trail hikers, on multi-day trips, carry closed cell pads now because of simplicity, speed of deployment, reliability, weight, insulation, and price. All good reasons, and that is what I do on that kind of trip. However, the bulk and shape of a closed cell pad can be an intereference for some types of trips where you are wearing a pack off the trail, and need agility and a small pack profile, such as hunting, fly fishing, or scramble-climbing. For these trips, an inflatable torso pad is much better for reducing pack size, but adverse to moisture, and I am already carrying a garbage bag. Even now, some people are willing to deal with the prices, delicacy, an fuss of inflatables for their comfort in on-trail hiking. In a few years, as prices go down and durability goes up for insulated inflatables, closed cell pads may have gone the way of external packframes.