From what I understand, this sort of thing is common in departments as diverse as English, math, and various foreign languages; the reason is that those departm

From what I understand, this sort of thing is common in departments as diverse as English, math, and various foreign languages; the reason is that those departments tend to teach a lot of low-level courses, so they need a lot of TAs. (I'm a PhD student in a math department, and my department doesn't do what you describe, but some of the departments I considered were like that which is why I didn't ultimately choose them.)