Hi Pika.
Yes, we had a similar experience. The Grand Canyon hikers we saw were way behind the curve somehow. They carried packs in hot weather heavier than I would take on a snow camping trip. Some of the sleeping bags I saw strapped below external frame packs must have weighed 4 pounds or more, twice what is needed there. When we talked to some of the hikers it was evident that while they were really liking the trip, that they had little experience. It is interesting that a trend (like lighter weight backpacking) takes so long to develop. Many manufacturers still sell 6 and 7 pound packs and tents for example.
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Jim M