BeBop, the rationale is indeed that many bidders do NOT bid their true maximum. The bidder who bids half what they are willing to pay and thinks they're going to get a great deal is at the mercy of the sniper.
Secondly, while cheating on eBay may not be rampant, it isn't rare, either. I've seen auctions where the seller under another name, or a friend of the seller, bumps up the bid incrementally until the other bidders max is revealed, then cancels their bid that passes it because "it was a mistake". The bidder may not be bidding against anyone, yet still pays their max because of cheating. Sniping eliminates this possibility.
And it may seem infantile to you, but for most bidders, winning the auction is actually the point...
(Edited to add....)
By the way, my actual bidding is quite similar to yours. It's just that I make my bid through auctionstealer.com and let them handle the snipe. There's no monitoring involved. It's just bid and forget it.