Since phones have a lot of storage, then why not constantly backup locally and overwrite it for newer versions (opt in of course)? Signal already has large oper

Since phones have a lot of storage, then why not constantly backup locally and overwrite it for newer versions (opt in of course)? Signal already has large operating cost, so a cloud backup with the very low subscription cost is concerning. It would help Signal to get rid of sms registration and move to something less costy.