Spoken like someone who doesn't understand game theory.
There's two basic ways to look at an auction. From the seller's perspective, the goal is to extract the highest price possible. From the buyer's perspective, the goal is the pay the lowest price possible. So while it's true that you can simply put in a "maximum bid" and let the system automatically up your bid, it's also true that such a system is highly biased towards the seller's goal. If the starting bid for an item is $10, and two people have put in maximum bids of $30 and $35, then the bids will almost immediately jump to $31 (assuming the auction uses $1 increments). Whereas if both buyers played their cards a little closer to the vest they could wait until very late in the auction to up the bid from $10 to $11, and then take turns outbidding each other. Depending on how much time is left and how closely the auctions are being watched, it's possible that someone will be able to get a lower sale price using this method than if they had specified a maximum bid. So while the "maximum bid" feature is billed as a way to make things easier for buyers, it actually favors the seller by increasing the price more quickly than would otherwise normally happen. Of course, this also favors eBay as well since they get a percentage of the sale too.
Sniper bots are essentially the same thing, but they're designed to be smart enough to wait until the end of the auction to put in the bid. That might help keep the sale price down a little bit, but if your goal is the win the auction rather than get the lower price, it's probably more efficient to use eBay's maximum bid tool.
There's two basic ways to look at an auction. From the seller's perspective, the goal is to extract the highest price possible. From the buyer's perspective, the goal is the pay the lowest price possible. So while it's true that you can simply put in a "maximum bid" and let the system automatically up your bid, it's also true that such a system is highly biased towards the seller's goal. If the starting bid for an item is $10, and two people have put in maximum bids of $30 and $35, then the bids will almost immediately jump to $31 (assuming the auction uses $1 increments). Whereas if both buyers played their cards a little closer to the vest they could wait until very late in the auction to up the bid from $10 to $11, and then take turns outbidding each other. Depending on how much time is left and how closely the auctions are being watched, it's possible that someone will be able to get a lower sale price using this method than if they had specified a maximum bid. So while the "maximum bid" feature is billed as a way to make things easier for buyers, it actually favors the seller by increasing the price more quickly than would otherwise normally happen. Of course, this also favors eBay as well since they get a percentage of the sale too.
Sniper bots are essentially the same thing, but they're designed to be smart enough to wait until the end of the auction to put in the bid. That might help keep the sale price down a little bit, but if your goal is the win the auction rather than get the lower price, it's probably more efficient to use eBay's maximum bid tool.