At the very least, be aware they exist, it can save your land, your cabin, etc.
Ultimately, the defense of your property boundaries (legally or otherwise) falls on you.
I had the experience in California you are talking about. Before I sold my property, we had it surveyed to locate all the property markers. Seems the neighbor on the left had a fence about 2 feet onto our property, and the neighbor on the right had a rock wall about 3 feet onto our property.
The new buyer of our property had both fences moved back to align with the accurate survey. Everybody was satisfied that true boundaries were established.