"Epidemic" suggests that they number of such questions has been growing dramatically, but that's not the case as far as I can see. They've been with us for all of the year I've been using MSE.
There's also a lingering debate on how to deal with them. Many commenters are quick to chide new users for their use of the imperative mood specifically, which I think makes it quite difficult for those users to understand what the problem with his question is. After all mathematical style uses the imperative mood all of the time ("Let $n$ be an aribitrary integer." "Consider the function $f(z)=e^z-z$." "Proceed by induction on $n$", "Take successive square roots of the result until you reach an irrational", etc). There's nothing wrong with the imperative as a grammatical device.
What is wrong about the questions you speak about is that they consist entirely of a verbatim reproduction of a homework exercise, usually with no words at all spoken by the asker to the reader. This makes it difficult to gauge what it is the asker needs help with, and is demotivating for answerers because it looks like the OP is just asking us to cheat on his homework for him.
The relevant policies and FAQs do encourage users not to post questions that consist exclusively of exercise text. The problem is that many new users don't read that guideline, and it is hard to see what we could be doing to force them.
A different problem is that the users who ask these bad question often get fully worked solutions as answers. The question may be downvoted, but for a user who cares neither about reputation or about learning something has little incentive to ask good questions.