If you don’t have sufficient permissions to access a SharePoint resource you are presented with one of three messages. If you have Access requests activated for the site you will see something like this:
From my experience many people tend to think that this is just a plain error message and click it away, followed by an email with the question to please provide the necessary permissions to access the resource. They don’t *really* realize (or know) that they can send a request with a custom message which the admin will read and cause him to react accordingly. That means that the big advantage of sending a request in the context of a resource stays untapped and the email odyssey begins in which you (the admin) try to figure out what the user has just clicked right before this message appeared.