IDelete-MSG is a new tweak available on Cydia that allows you to delete all messages with a single button. The tweak will add a new button in the upper corner ner of the native application for the iPhone: Message, which will erase all your messages in one go.
S could be 'expected that Apple solves this problem with the iOS 6, but n has probably not seen this as an urgent problem or simply does not implement this feature for some reason. Fortunately the jailbreak community does a good job. The latest example of this work is precisely IDelete MSG-free available on Cydia for several days.
You tell me that it is useless but for several reasons you may want to delete SMS conversations. In fact, in some cases, the list becomes so long that it becomes difficult to manage, which is why this tweak could be useful.
After installing the tweak on your device, there will be no options to configure in the settings, but only one button in the upper right corner will appear. In the next update, the developer will add the ability to enable or disable the button that lets you delete all your messages and add the location in different languages.
If you are interested, you can load IDelete TV-MSG on Cydia Store, available free on the BigBoss repo.