Imagine you’re organizing a team outing next week. You add the actual time of the event to your calendar, and also add a few related to-dos, like booking a restaurant, buying company t-shirts, etc. onto your to-do list app. Then, oh no! There’s a team emergency, the outing will have to be cancelled this quarter. After removing the outing from your calendar, you need to manually track down the related to-dos on a separate app and delete them.