People who pay monthly for a planner app (Motion, Sunsama, Reclaim etc), what's the thing that actually makes it worth the money?

I've been burned before, spent hours setting up elaborate systems I abandoned in two weeks, so I'm skeptical of anything with a learning curve.

If you're paying $15-20/month for one of these: what does it do that a free calendar doesn't? And if you cancelled one, what was the final straw?