Inspired by this poorly worded question:
https://graphicdesign.stackexchange.com/q/104524 (now deleted)
Or this one:
Is it acceptable to ask about removing watermarks? If yes, what is the proper way to ask about this?
Off the top of my head I can think of three possible legitimate reasons:
The watermark was created by the author who accidentally deletes the original. Now he want's to know how to remove the watermark.
The work is abandoned copyright (grey area?) For example: The watermark could be a logo from a screenshot from an old TV network that no longer exists. Question asker could ask how to remove that watermark for personal non-commercial reasons.
Someone who just wants to learn a skill. IAMAL so the following statement may be incorrect. Correct me if I'm wrong. It would not be considered copyright infringement if someone downloads a sample watermarked image just for the purpose to remove the watermark. After removing the watermark the image is immediately deleted. The image isn't technically being used in any original work. Downloading a publicly displayed watermarked image to your desktop is not illegal as far as I know. Modifying it to learn a skill and then deleting it isn't illegal either. So, no law is being broken.
I think #3 might be the weakest argument I can make because I'm not a (US) copyright expert. However, I still believe there are some legitimate reasons to allow watermark removal questions like this. (If the question isn't worded as poorly)
For an example of abandoned copyright I have the following source. I know it doesn't have to do with art specifically but it proves that copyrighted material can be abandoned and even given a free pass to some extent. (again in my favorite color grey)
The Internet Archive has created an archive of what it describes as "vintage software", as a way to preserve them. The project advocated for an exemption from the United States Digital Millennium Copyright Act to permit them to bypass copy protection, which was approved in 2003 for a period of three years. The exemption was renewed in 2006, and as of 27 October 2009, has been indefinitely extended pending further rulemakings (https://en.wikipedia.org/wiki/Abandonware)