The problem is caused by a lack of popularity it seems among undergraduates.
Since history professors have pursued smaller and smaller niche subjects in order to have something “new and original” in their PHD dissertations, the profession has become more insular despite the claims of widening the scope to include all the niches beloved of the Social Justice Warriors.
I had a history professor tell me I should consider history as a major when I'd crapped out of my first major, problem was (as I told him) the janitor on my dorm floor was a four year grad with a history degree from that very university. He suggested that such people just didn't want to leave the university environment, but agreed that a minimum of a master's degree was needed to get anywhere, and a doctorate to teach. He also amusingly noted that a couple of his candidates were in Central America and he was going to spend Christmas break down there with them, helping them sort something out, mainly because of the risk that they might be changing to anthropology. :^)