Do Non-fiction Books Need Agents?

Do you suggest getting an agent for nonfiction books? Or sending the book proposal directly to a publisher?

Jump Start Your Writing Career With This Little Secret By Sheron Donahue

I devoured every page of my favorite magazine – the one I dreamed of seeing my byline in. Since divorcing and entering a new, sizzling relationship, even the Dear Amy column intrigued me.
A reader asked, “How can I get my boyfriend to stop kissing me in public?”
The answer I read would change my writing career.