While my degree almost certainly qualifies me to write articles for the most prestigious dick joke-themed websites, I'm probably less prepared to expound on the nuances of phlebotomy, even though I've totally done exactly that. The fact is, every word you're reading in that high school-level textbook was probably written by someone who is only a couple years older than you with approximately the same dedication to the subject matter. You're taking that class for a passing grade; they're writing that book for a paycheck.
"But you're working for a textbook company," you might be saying, "surely there were special resources available?" Yes, sometimes I was given some help, but the vast majority of the time, that "help" was just another textbook, most likely written by another textbook freelancer (a different, less attractive version of me). More often than not, all I got to work with was an outline, and outlines by their very nature do not contain content, just a list of subtitles that will fill out my chapter. I still have to find the information myself, and since I'm no expert on interdisciplinary research practices in the modern nursing profession (another actual topic), then here I go a-Googling; a-Googling I go.
"If it's good enough for Yahoo! Answers, it's good enough for Vassar."
Which is why we're getting fourth grade history textbooks that claim slaves fought in the Civil War on the side of the South. Some overworked freelancer based their research on a racist source, and no one bothered to fact check. Because ...