This view is a few years old, so things might have improved since then. That said...
The main benefit is that you can join an education program as a professor and in turn train other graduate students to get THEIR PhDs in education. That's the primary purpose of the degree. If you are not a good enough cloner, you can use the degree to climb up administration ladders.
The modern education PhD is one of the purest Ponzi schemes in the history of academia. While all academic disciplines' PhD programs are at least partly about creating clones to carry on ideologies, in education, this aspect overwhelms everything else, mainly because a single ideology appears to have held the discipline captive for a while now.
Practical matters like improving education, understanding learning processes better, training better teachers... these mostly take a backseat to the propagation of ideology. They are nominally considered of course (and in fact, nominally they are the main topics of discussion), but in practice, they become vehicles for other motivations.
I have no axe to grind here. I happen to have a PhD (in engineering), and during my many grad school and postdoc years, I met dozens of other PhDs in other disciplines. The education candidates were the only ones who struck me very forcefully as being on some sort of Stepford PhD assembly line. They creeped me out.
With people from the other discplines, everything from archeology to zoology, I got along with perfectly fine. Regular, smart, critical-thinking people from whom I learned a lot, and who were interested in learning from me. With the education PhDs, unless they were very new to their program (and therefore incompletely indoctrinated), you couldn't hold a conversation. They only wanted to teach you their ideology, and convince you that you were teaching your classes all wrong. Hmm... maybe that isn't so surprising.
The specific ideology holding the discipline of education hostage appears to be some vague mishmash of promoting diversity and fighting oppression against women, minorities, Bambi and little furry green things from Betelguese, and railing against Dead White Males. It also involves repackaged Marxism, and unprocessed postmodern mumbo-jumbo.
Note that I have absolutely nothing against postmodernism. I like it very much in fact, and enjoy PoMo ideas in other fields like anthropology, literature or sociology (even of they DO star the well-known Dead White Male); education is one of the fields where it turns into incomprehensible mumbo-jumbo).
It doesn't help that the education PhD is also very commonly a part-time occupation of harried practicing teachers hoping to grab a credential to climb some administrative ladder. They are generally too busy to critically question the ideologies being shoved down their throats, which makes the standards of debate and healthy dissent in the discipline far lower than in other disciplines.
This is politically incorrect of me to say, but a lot of them are also from the very "oppressed" groups whose oppression is the ideological concern of the field. So confirmation bias grabs hold, and it is pleasanter for most of them to grab hold of, and preach themselves, an ideology that just happens to validate their own sense of oppression. In this trade of convenience brokered by moral hazard, the little matter of inquiry into the subject at hand doesn't figure very prominently.
Compared to the fishmarket that is the typical academic discipline, education appears to be a strangely peaceful domain, where one pet approved-by-the-Inquisitors theme du jour after the other produces a cohort of PhDs, parroting the right party line about that theme: be it active learning, cooperative learning, the "scholarship of teaching and learning," outcomes measurement, etc. etc.
If you object, you get cut out and shut down so fast, and so comprehensively you'll wonder what hit you. I found out the hard way by raising what I thought was an innocent and reasonable debatable point during a seminar organized by the education types...
Miraculously though, through this mess, some actually interesting research on teaching and learning accidentally breaks out once in a while.