This is Important!
Students need to know the importance of the material they are learning: buy-in and relevance. At the middle school level, students are beginning to enter into the developmental stage where actions have consequences: students can plan for the future by altering their current status.
By alerting the student population to the relevance and importance of the intended learning objective/s, the teacher has already planted a seed to future engagement.
Give It Context, and Make It Count
Studies published in the journals Nature; Science; and Mind, Brain, and Education support this idea, and a solid amount of research also links personal relevance and emotional engagement to memory storage.
Students need a personal connection to the material, whether that's through engaging them emotionally or connecting the new information with previously acquired knowledge (often one and the same). Without that, students may not only disengage and quickly forget, but they may also lose the motivation to try.