I've noticed that, too. I think I've stumbled across two separate cases out of New England recently where two little girls haven't been seen in over a year. No one can pinpoint the last time they were seen, and their families, in the meantime, are going about their day, business as usual, raising other children, like it isn't even their deal, or no big deal they're even missing. It was extended relatives who noticed they were gone and reported them missing.
I've also seen this a lot with historical missing women cases and their significant others. The SO's claim they got in a fight and the woman did one of two things: they either got out of the car in the middle of nowhere or simply vanished from the house in the middle of the night while the SO was sleeping. And law enforcement seems to just shrug and say "Okay, we'll buy that," and don't pursue it. Then the guy goes on his merry way.