From what I've seen discussed, it seems some percentage of "sniping" is to attempt to obtain both "winning bid" and "lowest possible price" (note, not the same as "max willing to pay for the same item"). The sniper is trying to hide interest, so as not to attract other interested bidders, and therefore grab "a great deal" of a small increment above the starting bid price.

And this probably appears to work enough times in the snipers favor to trick them into thinking it is a winning strategy, whereas they likely would have won the same auctions in the end by just bidding that 'minimum' as their maximum bid. But as they can't easily (i.e., without expense) A/B test their strategy, they get no feedback that sniping isn't really helping them like they think it is helping them.