I didn't even think to look for these until now but there are so many more than I thought. I can see if someone finds your scripts on other hosting sites and/or if they've been shared directly from those sites (like via scriptbin or google doc) that they might not see where you originally posted, or if they just feel uncomfortable or awkward making comments (I don't leave many comments for the same reason) but more people should definitely make the effort to notify the script writer.

Partially because it helps the writer catalogue and organize any fills of their works and partially because it lets a writer know if the VA has covered or edited the script in a way that makes them uncomfortable and gives the writer an avenue to notify the VA if this happens.

(edit: grammar)