Some people will just not be bothered to edit or update their threads. I've had several successful job completions in the Paid Requests and even have requested the Client to update their thread with my site information and details of the job ==> the greater percentage have not even done that.
And while the obviously cordial thing for the OP to do is to update their threads - It would basically be impossible to huntdown and force every single poster to update their threads; Some people are lugheads who cannot be moved to do such a thing

--- Then at the same time if such a policy were implemented - The vB.org Staff would be too damn busy to do anything else. So - adding such a force update/edit thread policy is a bad and almost impossible idea to add to the already bloated list of vB.org rules.
Jacquii.