Steam really doesn't need to pricematch.
Here's the argument:
Steam is too used to being the only successful distribution service out there. They should start pricematching other sites so that instead of these deals helping draw in customers to alternative services, it gives people even MORE of a reason to just stick with Steam.
Steam soon drives all it's competition out of the market thanks to being able to beat any price they propose. All the competition goes away, Steam goes back to charging whatever the hell they want.
Edit: Alternate outcome scenario: Games start becoming service exclusive. We've already seen EA going that route.
BTW, when the hell is the Summer Sale going to start. I have money to burn. I want to burn it.