Contrary to popular belief, snipe is not caused by the bed or tables, but by the drive rollers of the head, which indirectly causes flex in the rest of the machine. This is why sniping always occurs at a precise location on the workpiece, which is equal to the distance between the cutter head and the infeed/outfeed drive rollers.
In simpler terms, snipe is the opposite of what most people think. It isn't a thinning of the end(s) of the board, but actually a thickening of the center of the board. When both infeed and outfeed rollers are in contact with the board, their downard pressure pushes up on the head and/or down on the bed (depending on whether the planer uses a fixed bed versus adjustable bed). In other words, the bed and the head get pushed apart while the center of the board is passing through, but relax slightly when only one of the rollers is applying force.