Why are “Messages in iCloud” still taking up storage on my Mac if they’re supposed to be in the Cloud? I have all of my messages stored in iCloud, but for some reason they’re still taking up SSD storage on my Mac. This behavior doesn’t happen on my iPhone, but it does on my Mac and I’m not sure why. If they’re in iCloud, why are they still taking up the internal storage on my Mac? It seems strange that my iPhone doesn’t store messages on its internal storage, but my Mac does. Is there a way to prevent this from happening on my Mac somehow?
iCloud Messages is a synchronization tool, not a storage tool.  On either platform, it will download messages to the local device, and eject them again, when necessary.