Jim, this is not a personal attack at you, and thanks for showing examples of lead pencils that have been found.
However, pencils made of lead were about as commonly used as quill pens by the time of the Civil War. The pencil making business took off in the 1830s with the ability to manufacture pencils with graphite clay (still used) as the inside of a pencil. One of the more notable pencil manufacturers was the Thoreau family of New England, and their success allowed their son, Henry David, to sit around at Walden Pond writing instead of working for a living. See this link for his pencil making prowess...
The reason that lead pencils are found in campsites and wooden ones are not is simple. Wood rots. Lead doesn't. Again, I'm not being nasty here, but we could also draw a conclusion, based on strictly archeological evidence, that labels were rare things to find on bottles, because every time a bottle is found there's no label on it.
And that James Townsend mechanical pencil: That's a Porte-Crayon, and even in the 18th century, it was considered an artist's tool, and not really a mechanical pencil. This is the type of pencil that artists use to make pencil sketches. It used a relatively thick stick of graphite so that thick, thin, and shaded areas can be drawn.
By the way, if you've ever tried to write with a lead pencil, i.e. made of lead, the line is very light. That's one of the reasons that graphite was so preferred over lead as a writing medium.