1. It makes you look "green" because people don't do that, so it looks like you just stepped off the bus and thought it was appropriate to put your picture on a resume.
2. They might not like the looks of you. Despite giving people the benefit of the doubt, there are still those who "judge a book by it's cover.
3. You may remind them of someone they don't like, appear to young, or too old. Bottom line, you just may not look "the part" of whatever they think your classification should look like.
Now, the ONLY exception, (and I even think this trend may be over) is actors putting their pictures on their resume. But, before you do, check in with casting directors, agents & managers, and working actors to see if they're still doing it.
For more tips and articles by top entertainment industry career coach, The Greenlight Coach, visit www.theGreenlightCoachBlog.com