Keeping in mind that all of the accumulated data is anonymous, there isn’t some universally important reason to reset the Ad ID and by no means should it be considered standard procedure. Reasons why you might want to reset the Advertising Identifier For example if you have every Angry Birds app installed on the device and do 100 web searches for Angry Birds a day, disabling ad tracking would prevent you from seeing ads relevant to that topic.
What that will do is completely deny the ability for anonymous data to be gathered about the device to serve more relevant ads, outside of web cookies. You can also go the extra mile and turn iOS ad tracking off completely while you’re at that settings screen, which functions like a “Do Not Track” feature and prevents any of anonymous data accumulation from happening. Once confirmed, iOS will regenerate a new random blank ID. Scroll all the way down and locate “Advertising”, from there tap on “Reset Advertising Identifier” and confirm the ID reset.