What does Syncing iMessages to iCloud actually do?

On iPhone and iPad, if I go to Settings -> AppleID -> iCloud there is an option to enable iMessage to sync to iCloud under the apps using iCloud section. My question is what exactly does this setting do? The description on my iPhone and iPad for the setting says "Sync your messages to iCloud so you can continue your conversations from all your devices." However this feature works without enabling this anyway. I have this setting turned off on all of my devices but I can still send and view up to date messages in iMessage on all my Apple devices, and everything seems synced. Interestingly enough my Mac does not have iMessage listed under the "Apps using iCloud" section so I cannot enable this setting on my Mac anyway. So I do not see the benefit of enabling this setting since all it does is just take up space on my iCloud. Is the description for this feature misleading? Is the point of this so that my messages are retained in the event that my devices are compromised?

EDIT: So I just realized the setting is also available on my Mac. It was just hidden beneath the iCloud app. Interestingly enough this setting was turned on the whole time on my Mac but it did not take up any storage on my iCloud. When I turn the "Sync this iPhone" or "Sync this iPad" options on my iPhone or iPad for iMessages, the iMessages take up around 5 GB of space. For some reason the Mac does not take up any space even though the setting is enabled.