The big question is. Why didn't the South Carolina local and State Police act more quickly? Why did it take the NYPD to coerce the NCSP into starting a search and get the FBI involved?
Now you are starting to ask the right questions...
Because it isn't against the law for adults to go missing if they want to. It's also standard protocol for LE to wait 24 hours on missing persons reports for adults.
Just because we don't *think* our parents would disappear on purpose, or our spouse or brother or sister or in-law or grown child would, doesn't mean that they wouldn't.
The privacy factor is built in here, primarily because of abused spouses or family members who need to get out of a dangerous situation. That is the extreme, but that sets the bar for determining whether an all-out search will commence.
This is why the HyPo won't give out details on car accidents or the the hotel in Portland wouldn't give out credit card info on the Kims. As a private citizen, you have to make a very strong case of "probable cause" to get LE to help you.
It's sad that it has to be this way, but it does. It has saved many lives in the long run.