This lets students know that this is a serious, important assignment. To not do so signals students it is not important. The Rule of Pretense . Whether it's true or not. An Addendum .
Homework is a cultural statement.
Whether your students plan on doing any homwork or not, they expect to be assigned some. It tells them you care about them. It tells them what you are expecting of them is important. It offers them the comraderie of facing your unrealistic expectations together.