Apple has to at least appear to un-do the unlocking.

They have these different carriers in different countries vying to carry the product, locking people into contracts at prices higher than people are used to paying (especially in Europe where prepaid plans are more popular).

So in order to get favorable contracts with these carriers, they have to appear to try to keep people in these contracts.

Same way they're probably not too crazy about the ring tone pricing so they make it easy to hack but once it's hacked, they have to try to undo the hack to placate the RIAA.