You must, to the extent reasonably practicable, remove the information specified in (i) – (iii) above if requested by Licensor.
The idea is that a person can remove their association with a derivative to protect their reputation. At least that is what the theory is, as Andrew Rens points out:
I’ve advised many potential users of Creative Commons licences who are reluctant to use Creative Commons at all, or plan to use Creative Commons Attribution No Derivatives because they are concerned that their reputations will be irreparably damaged by a remix of the works which they license under Creative Commons. Most have been sufficiently reassured by the provision which allows the licensor to require that the Attribution be removed to use CC By SA and CC By. If this provision is removed then many of those Licensors will choose to use CC By ND, or not to use CC at all.
I completely agree with eir assessment, from my own experiences; visual artists in particular have strong reservations about using various CC licenses, for an array of reasons. I say that is the theory because it doesn’t make much sense to me.
Accurately depicting reality is important to me. As such, it is an affront to my sensibility that someone would keep factual information about a cultural work obfuscated. I understand the need to present the status of endorsement, because that too is accurately depicting reality, and assist us in navigating qualitative decision-making; the first thing that comes to mind is politics, as gross as that is.
I acknowledge that clause as is, Creative Commons has a difficult job of balancing between supporting current practices and viewpoints (so as to not be rendered irrelevant) while also progressing toward a saner, freer commons. Theirs is an open process, as well, demonstrating the transparency that I hope will one day be embraced as a norm.
Besides, it makes it easier to parody hateful or distasteful remixes if we know where the source material came from. ^_^