I've heard the same -- both because of the danger and the desire for solitude. Thru-hikers may not want to handle all of the questions and bonhomie from weekend hikers who are in the shelters.
However, aren't you allegedly 'required' to sleep in shelters rather than along the trail?
No not at all. I have never stayed in them except one time when they built the new loft models. Many reasons, but mice being one of them. Also, we always liked to get off the trail and have a sense of solitude and/or better views. I have met some real wierdos out in the woods. Another reason to stay off trail and out of sight.
No...you don’t have to sleep in shelters...except for the Smokey Mountain part of the trail....I don’t like to sleep in shelters myself...too many mice and it’s warmer in a tent anyways...the best advice i have is be aware of your surroundings but it is hard to do when you have been hiking all day and negotiating rocks and roots....really the best advice is don’t go alone...always hike with a partner for many good reasons.
....However, aren’t you allegedly ‘required’ to sleep in shelters rather than along the trail?....
No. In National Parks and some other controlled areas, but on much or the trail water is the controlling factor.
Some thru hikers stay in shelter to avoid carrying a tent, but others shun them because of people who stay up all night.