They show up in my e-mail box: documents that require review or grading, and they still don't have cover notes that explain their presence.
Each time it happens I see that character played by Meryl Streep in The Devil Wears Prada dumping her coat, day after day, upon the receptionist that she notoriously abuses in all kinds of ways.
When someone litters my email box with an attachment that does not have an explanatory note, I feel the same way I imagine the character who played the abused receptionist feels: as if I am doing someone else's laundry, and it's not my job. I am not the receptionist, but I am treated like one when someone dumps a document in my email box, like a piece of clothing that needs to be hung up on a hanger somewhere else after I have cleaned and pressed it.
But aside from the admission that I don't like to be dumped on and this causes me to feel no small amount of irritation, I feel greatly sorry for the person who sent the message who might be sending other more important messages (or even resumes) in the future to people who could hire him/her or promote him/or her. Ideally, that recipient might also be inclined to think highly of the person for demonstrating consideration of others' needs and time by simply explaining the presence of the document that has been sent.
In short, not writing a cover note for attachments via email is not only very poor salesmanship (poor customer relations), it's worse: it makes you look really bad. And whether you understand this or not your name becomes associated in the minds of others as rude, self centered, lazy, late and a problem that you have to work around.
So, think about that the next time someone has asked you to provide the work that was expected of you; and after you have been asked, once, twice, or even three times, don't just finally send the document without the courtesy of a note that says, "Here's what you need." You could even go that extra mile and apologize for holding up someone else's schedule by not doing your job in a timely manner. You don't actually have to say that, but a general apology that has taxed someone else's patience is a good idea to cover the multitude of infractions that may remain unsaid in that exchange because even as I write this entry I am not saying everything I feel and think about inconsiderate people who live in the center of their universe where the people around them aren't coworkers--they are the people who clean up after them.