There's a lot of good research out there discussing the benefits of value stocks. Two people who write about it often are Larry Swedroe and Bill Bernstein, so if you're interested you might want to search for their books and articles. (edit: +1 to MustacheAndaHalf for the Swedroe recommendation)
That said, it's definitely a hotly debated topic. For example, even though the historical value premium is well documented some people reasonably question whether recent advances in technology (enabling easy value screens and index funds) have minimized one's ability to practically benefit from it. When value stocks become popular and easy to identify and buy, their price may become less of a value.
BTW, it's important to distinguish between active stock picking strategies (that often use value metrics) and passive asset allocation using value index funds. Many people may naturally discourage the active version but be more open to the passive asset allocation variety.
IMHO, value index funds can certainly play a nice role in a diverse asset allocation. It's not required, though, and a total stock market or "blend" fund (that also includes value stocks) is just fine.