The greatest thing about seventh grade spelling words is the same thing that's wonderful about all of language arts in the seventh grade: utility. For the first time, learning English is not just for learning's sake. The things students learn in the seventh grade, including spelling, are important to the daily lives of ordinary citizens.
They will start gathering facts and coming to their own conclusions on important issues, the kinds of issues about which individuals have different opinions. Indeed, if you want your students to take anything out of middle school, you'll want to impress upon them the importance of what they learn on their future selves.
Sure, convincing students that what they're doing in school has real-world applications is always challenging, but it has never been more true for students before the seventh grade. They are becoming adults, and their spelling skills will reflect that. In a way, they are becoming individuals. Figuring out who those individuals are turns them into introspective detectives. It is a very thrilling time for all.