First, you are obviously looking at things from the perspective of an accomplished photographer and not the perspective of an amateur enthusiast, beginner, or long time hobbyist. I think one of the reasons so many people take photography workshops is very simply for camaraderie. Like you, I personally would much rather shoot by myself than in a group, but based on the things I've experienced, I believe we are in the minority. People love to talk about their passions and greatly enjoy being around people that share their common interests. For many, this alone is worth the $1000 price tag for a workshop. Others may have not visited the location of the workshop before and simply want someone else to do all the work of scouting and to bring them to the right location at the right time. Some people may feel so intimidated and overwhelmed by the idea of going to a location that they find it easier to pay someone to hold their hand. Also, as Kerstin mentioned, for many they simply go for bragging rights. While I do not agree with any of these things, it's impossible to hold others to the standards that we set for ourselves and we must remember that people's goals will almost always be different from our own.
Now, in my opinion, the job of a good teacher in this situation is to INSPIRE. Let's be realistic - photography takes years of hard work and practice to master. How much are you really going to be able to TEACH in 3 or 4 days? Not much at all. If you try to teach a group, odds are all you're going to do is entertain them for a weekend after which they will go home and promptly forget all they learned. By using a workshop as a catalyst and the time to inspire the group, perhaps you can get through to one or two of them who will go home and continue their education and learning process. I feel the only way to make this happen is to clearly state the goals and purpose of the workshop up front so as to minimize misunderstanding.
On the issue of integrity and locations. I don't know that there is a good solution. As explorers, it is in our nature to seek out places less visited and uncover secrets, but lets face it, explorers by their very nature are not going to take a workshop in the first place. Personally, I believe that large groups should be restricted to well trafficked areas to minimize impact on the environment. Many of the people taking a workshop have not visited that location before and will likely be pleased to visit the major highlights. Again, this is about being up front and honest - these are the goals of the workshops, this is the purpose, these are the locations we're going to visit. If stated up front, those with goals different from that of the workshop will simply not sign up and those who do will be like-minded.
Bottom line, love them or hate the, photography workshops are here to stay. I hope the NPS continues to crack down on photographers who violate the rules. The more people are educated about what these kind of topics, the more things should improve. Unfortunately with the aid of the internet and the easy to use digital cameras, the term "professional photographer" is no longer based on prowess but on popularity. Such is the world we live in. Hopefully the future will see more people who embody the true meaning of professional lead the way and inspire those new (or old) to photography to learn things the right way, protect the environment, and have integrity and pride in the things they do.