But if it ends up in the spam folder there's at least a chance that it'll be trained out of the spam folder by people marking it as "not spam", and it provides a workaround for the people who really need it to work _now_.
My mother would just simply ignore the spam and often times spam catches majority of the phishing e-mails too. So it's a double edge sword educating and conditioning the users to review the spam folder. Why is it the end user's job to determine what is spam and what is legitimate ?
Who else could determine that? I could hire you to send me emails about Viagra sales. They would not be unsolicited, because I specifically asked you to. They wouldn't be commercials, either, so they wouldn't be Spam. An automatic filter can't determine if it's spam or not, it can only take an educated guess.