Despite all subsequent owners claiming not to have experienced anything weird, no one seems to stay there for very long. Sure, people move all the time, but it's an absolutely exquisite building and property in a nice area.
No one ever decided that it would be a nice place to grow old in or at least keep it for as long as their children are minors? No rich horror or occult enthusiast thought it would be a good vacation home?
The Cromartys and O'Neills lived there for ten years each. Brian Wilson lived there alone for thirteen years. The D'Antonios have been there for five years now with no signs of looking to sell. Four sets of owners in nearly forty years isn't that strange for most neighborhoods. The family that sold it to the DeFeos had lived there for five years.
If the average length of ownership of the house since the murders and alleged haunting is significantly lower than the average length of home ownership in the neighborhood, it probably has more to do with the notoriety and being bothered by annoying gawkers than anything else.
Americans move, on average, ten times in the course of their life and more than 10% of Americans move each year. So, people who "grow old" in the house where they raised their kids would seem to be in the minority.
The house has been renovated so extensively in the last few decades, it bears little resemblance to 'High Hopes' or how it was during the alleged haunting so I doubt a hard core occult enthusiast would find much value in it in it's current state. Since the town itself hates the notoriety of whole thing, they probably wouldn't even allow it to be sold to someone who would embellish anything about the era or draw attention to the murders or the haunting. The town would probably buy the house itself to prevent a spectacle like that.
What many forget is not everyone can see or hear spirits. I’ve have seen and heard them all my life. They are all around us and very active. But the simple fact is only a small handful of us have the “gift” or I guess sensitivity to know they are here.
If you read any story of a “haunted” home or place there is often the claim of “recent home owners have not seen or felt any paranormal activity.” That doesn’t mean the former owners were liars. That means either evil spirits followed the old owners or they don’t care to bother the new ones.