Using another person to write an assignment is unethical, according to The Atlantic. The ethical issues stem from a student possibly not mastering the course criteria and passing off another person's work as his own. The lack of credit given to the real author also proves problematic.
A student who contracts with someone else to write an assignment is cheating instead of furthering himself intellectually. The paying student does not need to contribute rough draft ideas or anything except a topic, deadline and payment. Some reasons students may farm out their assignments include a lack of time, too many commitments, and balancing work, school and family responsibilities.