One issue that came up frequently in the forum is that Joplin's data can be very large, especially when the note collection includes many attachments (images, PDFs, etc.)...Joplin (Desktop, mobile and CLI) attempt to mitigate this issue by providing an option to change how attachments are downloaded during synchronisation.
In 2019, Joplin rolled out a useful feature to help with "saving disk space and network bandwidth, especially on mobile". This very useful feature lets you change "Attachment download behaviour" to always, manual, or auto. The setting is Profile-wide.
As Joplin matures, and folks use Joplin for longer, we're going to encounter more scenarios where the storage consumed by Joplin on mobile will exceed available storage.
Then you'll have users run workarounds like this, where they periodically delete and reinstall the Joplin app, to reset the storage usage to a level that fits on their device.
So, the ability to control attachment download behaviour at a Profile-level may not be enough.
Yes, storage is cheap. Speaking relatively. But it also happens that while there may be surplus storage on Joplin Cloud, and maybe one's primary mobile device, a secondary device can have far less storage to spare.
As an example, one way to address this could be allowing the existing attachment download behaviour to be set at a notebook and/OR tag level. A user could have notes in one notebook always download attachments. And in another notebook, notes download attachments on-demand i.e. on auto.