They will not choose to write it. Would you work on something consistently if nobody cared about it?

There needs to be a reward for doing essays. That reward can be emotional eg. "the teacher I respect liked my essay" or "my essay was read in class" or "the teacher gives feedback that makes me feel a sense of growth". In that case, maybe kids will do it.

However, I think it's hard for a teacher to inspire respect to a classroom and the difficulty scales with the number of people in the class, so grades are used as a hack.