I'd submit that people gravitate toward that which is proven reliable and repeatable in the environment it's to be used in. And you have to throw people's own experience, level of skill, and confidence in performance into that equation. If someone has stayed dry in a tent, and knows that others have as well, why would they change without gaining a significant advantage for taking that risk? It's not that a tarp is a bad choice. It's that it isn't always the best choice given the need for reliable performance by any unique user. There's little difference in weight between a tarp + bivy + groundsheet vs an integrated tent design of similar materials. If you like challenging yourself in unusual situations to hone your skills, that's fine. But for many, if not most people, the overriding purpose is to reliably stay dry, not to challenge their skills to see if they can or can not stay dry while in the middle of a hike, while wagering possibility of a very wet experience ruining their hike.
1) From all evidence I can find (hiker surveys, pics, etc), tents outnumber tarps on western trails as well.Lets be real. Many on WB are easterners with the main focus the AT. The AT is easy in many ways with it's massive uber analyzed and available infrastructrure. That ease creates a wider mindset of ease, comfort and convenience and it also influences ease of shelter choice. That mindset of familiarity, comfort and ease carries over to expecting it elsewhere and repeatedly.
Grandma Gatewood(REALLY?) and Eric(Eric by his own in person accounts, he was a kid) were not highly skilled, as if it takes a great amount of effort to use a tarp effectively. That's an excuse, an excuse so not to have to make an effort. Fine, don't make the effort, but don't blame it all on the tarp for the tarp not being the choice in the east and specifically the AT or LT.
2) While not skilled when they started, I would imagine by the time they both finished their first thru, both GG and ER had learned a thing or two. But that isn't the point regarding them being outliers. They hiked in a different era. GG in 55? ER in 69? You could count on your fingers the number of thru-hikers on any trail at that point in history. Thru-hiking wasn't mainstream or even common by any stretch of the imagination. Tents were pretty heavy back then. GG is an interesting story. Only took a shower curtain originally because she thought there were cabins waiting at the end of every day's hike. So, yeah, she learned a lot about tarps fast. And ER's 80 day AT hike was even the FKT for a while I believe. He wasn't your average hiker. Back then, tents were heavy (a "lightweight" Eureka Timberline was 7 lbs - and expensive in its day), and shelter space was much easier to find on the AT. So much so that many of us didn't carry a tent, we only carried a tarp or tube tent as a backup. Then, as it is now, it was about function and weight and need and anticipated use. When they were originally built, shelters were the answer to the problem of heavy canvas. Yes, they are now a holdover in that sense (would they have been built if today's tech existed back then?) and are part of the unique culture of the AT, as are the concentrated camping areas around them. Some hate them, some love them. But, they tend to attract lots of hikers when limbs and dead stand starts falling in a storm. They have their upside as well.
3) I don't understand the ongoing diatribe regarding "lack of effort" and "easterners". It's as though you have an overriding agenda to prove some closely held negative opinion you have formed regarding eastern hikers vs western hikers. I've met hikers from both coasts and the middle. Their similarities, skill levels, etc, far outnumber their differences in my experience.
Different gear works better in different environments. Would hammocks work on the CDT? Or in the Whites in NH? Lack of trees is a defining issue. Both are places where free-standing tents are good shelter solutions. But a tarp only strategy can be problematic in the Whites due to terrain, platforms, etc. Been there, done that. I've set up tarps in the Whites, and it's absolutely not the best shelter solution even with the extra effort I supplied. How about alcohol stoves vs canister? Alky definitely takes more effort and skill. Does that make it better everywhere and at any temperature for any purpose? No. It's not all about people's effort or skill. It's more often than not about suitability to the environment and task.Damn well right HYOH. Use what shelter you want. But do not imply a tarp is a BAD choice because it rains.
If you want to talk about effort look at the extent hammockers make. They make hangs as shelters adaptable to a wide range of conditions. That community always is advancing, evolving, not afraid. They don't get complacent. There's always something new coming out of that community. If we don't ever move beyond AT norms we become complacent. That's part of what we're dealing with- complacency.