The ones up by the Morphew house and on Monarch Pass were said to be traffic monitoring only (no pictures).
However, surely there are some in the larger area that do record?
I share your speculation, although I don't think the decor is exactly low key. I think the leather chairs and sofa are super expensive (by my middle class standards). I have friends with fairly nice houses, but nothing near as well decorated as the Morphew home. Of course, I'm probably swayed by the architectural details of the home. At $1.5M, it certainly should look great without anything in it.
I have friends who live in mountainous/upland parts of California, New Mexico and Utah (and family in Colorado). To me, that house is flashy. My best friend designed a house in pretty much the middle of nowhere, but she was at the time a 45 year resident of the area, and definitely designed a different type of home. She didn't want to attract attention to her home, including from neighbors. That's partly because she travels a lot and she and her husband travel separately a lot, so she is home alone. She wanted a certain kind of driveway and views of the only approach road. None of the main living areas are visible from outside the house, except the kitchen window at night. She moves vehicles when her husband isn't around, and makes sure one is always in the driveway. While she doesn't socialize much with her neighbors, they do keep an eye out for each other. Her family members have those neighbors' numbers in their contacts. She has an alert dog. No triple car garage, nothing like that.
Where I live, all creek and riverbeds are currently transit areas for homeless people (and the nexus of those trails/creek areas is vast - people can go as much as 30-40 miles up and down the riverbeds, always finding some source of water, and digging through garbage in nearby housing areas). Among the homeless, there are a certain number of people attempting to evade the law for various reasons, and arrests made on a fairly regular basis (but this is over-crowded California). Still, the same is true in counties like Mariposa and Madera in California, where living more or less "on the land" attracts a lot of people who we can call marginal to society.
But your point - that the Morphews seem very well off - is definitely a strong one. It's not a minor point, because people who do various kinds of stalker-like or home invasion things do select homes based on certain characteristics (lack of dog is one of them). In my suburban neighborhood, most of our houses are single story tract homes, but there were much bigger 2 story homes at the top of the price range - and those homes are in fact targeted more for daytime burglaries. People with more expensive cars in the driveway also seem to be targeted. We have an active security camera that is pointed directly at the only route to our front door (and a fence line camera in the back - both of those blink quite nicely at night).
If it's true that the Morphew house only occasionally had its security system working, it could have been an attractive target. To someone looking in through those windows, it would look quite luxurious, especially if that person was living rough.
(Just riffing off your post to throw another theory out there...)