Why should they have? It doesn't take 'mastery' to pass a class, it takes proficiency. Expecting perfection in all previous classes from students is silly.
>Many of the students aren't all that motivated, and resented me for asking a lot of them.
Are you teaching Math majors? If not, of course they aren't motivated. Most of them won't be using calculus in their daily life, they don't see it as valuable. Why should they, either, if nobody is presenting it's value?
Your post isn't a bad one, I just find a frustration with professors who forget sometimes that not everyone is interested in their subject. In an ideal world you would only teach people who want to learn your subject, but this is not an ideal world.