I have been to these places and asked myself the same question. "Why can't I build this?"
The one near the ranger station is so cool. She has a little garden and a nice small shack. I wish I could do this instead of having to make a larger settlement. My last two characters both made a little home down by the river as close to the border of SH as I could. No one visited since it was so far out of the main area. It was nice.