Some of the people that got outbid posted new bids at higher levels of price. It was perfectly normal to do so.
But when it comes to canceling auction bids, this always re-activate older bids and good faith buyers might find out in the end that they would have to buy more shares than they ever planned. What should they do, cancel some of their bids too?! Who is keeping track of all the mess? It would take weeks to sort this out and get firm confirmations from all buyers...
This is why bids have to be binding, the rule is logical.