A British man is ridiculously attempting to sue Apple following a divorce, caused by his wife finding messages to a prostitute he deleted from his iPhone that were still accessible on an iMac.
In the last years of his marriage, a man referred to as “Richard” started to use the services of prostitutes, without his wife’s knowledge. To try and keep the communications secret, he used iMessages on his iPhone, but then deleted the messages.
Despite being careful on his iPhone to cover his tracks, he didn’t count on Apple’s ecosystem automatically synchronizing his messaging history with the family iMac. Apparently, he wasn’t careful enough to use Family Sharing for iCloud, or discrete user accounts on the Mac.
The Times reports the wife saw the message when she opened iMessage on the iMac. She also saw years of messages to prostitutes, revealing a long period of infidelity by her husband.
You can sync your messages by enabling iMessage in iCloud. Or you can just not sign into iMessage on devices that are shared with other people.
It’s not broken, it works this way by design. If you don’t want your messages stored in the cloud, then they aren’t synced. This is a choice that many messaging apps don’t give you.