Alot of the MIA missions i went on were a bit of a mystery,why they were given MIA status when they were obvious "unrecovered bodies".
There are some really interesting LKA (Last known Alive) cases but many MIAs read similar to "...F4 on a strafing run was seen by his wingman to be hit with AAA, aircraft impacted at a low angle, no ejections"
And after many recovery team trips to the same site a small bone fragment or piece of life support equipment is recovered and the case is closed.
Letting the families think their loved one is MIA after all these years seems perverse.
On the other hand cases like SASless describes are so difficult to investigate as there are no witnesses to the final resting place.
In many cases Vietnamese witnesses will be found that remember "we buried him by a big tree" or such like and the search is on again.
"Last Known Alive" thats where the focus should be, and UXO removal.