Messages Taking Up MASSIVE Amounts of Storage?

Hi all, I'm really struggling trying to explain this issue to Apple's tech support and I hope someone can help me out here. I do not delete my text messages often, they're set to auto-delete after one year or something, but I've got enough storage space that it's not really an issue - they take up about 1GB on my phone, 40GB in my iCloud (a huge amount of this is photos and videos but whatever I have 2TB of space) and 60GB on my Mac's hard drive. In theory, my Messages should be synchronizing with my iCloud instead of staying stored on my hard drive, the same way as they're doing on my phone, right? Rather than taking up 60GB of space on my hard drive? I've tried disabling and re-enabling iCloud sync, but this did not help. Is there a way to delete them from my hard drive and keep them in iCloud where they belong? Thank you!