Pallets are the survivor's main resource in a chase. Dropping one puts a barrier between the two players, and if the killer is close enough when it falls, they are stunned for a moment. The killer can break the pallet to clear the path, which costs them time.
The strategic weight of a pallet is that it is finite. Once it is dropped and broken, that tile is much weaker forever. So a chase is partly a negotiation over resources: the survivor wants to extract as much time as possible from each pallet before spending it, and the killer wants to force it early.
This is why "when did you drop it" matters more than "did you drop it" at a competitive level.