Sprints are like cogs. They enable teams to organise dependent tasks. If you're happy to just say "We'll write the code for this when the designs are done, and

Sprints are like cogs. They enable teams to organise dependent tasks. If you're happy to just say "We'll write the code for this when the designs are done, and we'll finish the designs when the requirements are agreed" then you don't need sprints. If you want to say to people "We'll have this done in 6 weeks" then you need to have 'slots' where you can organise when the work is done. Those are sprints.