I run a web-dev consulting company on the side and I have a few apps that use Celery queues. The main reason you'd want to use celery is to handle more intensive tasks asynchronously in the background.
Some example from my apps:
- user requests a report: celery task is enqueued to generate the report as a PDF/CSV and email it to them
- admin adds a new user: celery task is enqueued to send an invite email out to the user, as well as some onboarding emails
- user requests to modify a large amount of items: multiple tasks are enqueued to update the items in batches of x amount.
I know this is off topic, but wool is a great book! If you haven't watched the Apple TV show I'd recommend it as well; they definitely switch up the story a bit but I've enjoyed it so far.