Disappearing messages can be great for privacy and I applaud them for that use case, but they can also easily be used to hide evidence of abuse and other nasty stuff right from the victim's phone.
I'd suggest a good implementation of this feature should come with a setting to disable disappearing messages by default (a setting which should be off). With the setting on, the sender should see the option to send disappearing messages be disabled, and the other party should be able to turn them back on on a per-chat basis. The setting should probably also allow tracking of edits/deleted messages. That way, people are in control and can know what to expect from their messengers. You won't find yourself lacking evidence of blackmail after the fact because your chat history unexpectedly deleted itself.
Furthermore, I think that most messaging within apps that provide this feature puts too much trust in the remote device. If you enable this feature, apps pretend that it's a sure and done deal, when in reality there are myriad ways of extracting messages before they're deleted.
As someone who bridges most of their chat apps through a (private) Matrix server, I've toyed with the idea of disabling the delete functionality to keep control on my side of the conversation. So far, I haven't needed it, but having the ability to do so if necessary gives a certain amount of comfort.