This is actually the primary explanation within the law enforcement community. People become so comfortable that they start to relax and become complacent. Slipping down a ravine, struck by a fallen tree or falling rocks, attacked and dragged off by a mountain lion, literally just not paying attention and getting lost, etc, etc. There's so many rational explanations for someone going missing, without even mentioning foul play.
However, the concept of someone labeled "experienced" that doesn't know about late stage hypothermia is ridiculous. Them then folding their clothing even more so. There's so many cases that were improperly investigated and reported on though, it's hard to know just how accurate a lot of the older source material is.