It should be obvious end to end encryption and ephemeral messages are for different threat models. And blocking iOS backup but allowing Android backup, desktop backup, and iOS history transfer is a really bad way to implement ephemeral messages.

You assume someone will know what they'll want later when they receive it. Saving several messages together is tedious in most apps. So is organizing saved messages.

Everyone that uses chats for serious business. I can't afford to loose conversations with my clients. For that I use only messaging systems that allow me to save chats: email, and then WhatsApp. Even Telegram has a problem, because even if messages are on the cloud, one could delete single messages or a whole conversation on your device as well.

Regarding screenshots and saving messages: not only it's a thing that you have to remember doing, but screenshots have (at least in my country) no legal value, since everyone can easily produce them with Photoshop. You can say the same thing for WhatsApp messages, but sure it's more difficult (or at least it appears more difficult to a judge that doesn't know anything about IT). Basically screenshots are never accepted as a proof for something, WhatsApp messages on your phone are.

And screenshots are not searchable

You don't know that a message is important at the time.

But the aim of Signal is default secure comms. It's supposed to easily wrap everything, from the absolutely banal to the fairly sensitive, in strong encryption in order to cut into the returns on performing mass surveillance.

The question just comes down to who generally wants their communication contents persistent until actively destroyed, as opposed to quasi-randomly wiped out by technical snafus.

If you want transient there are the time-limited messages, for instance...

I use signal to not be spied on by facebook or telegram or w/e. That is entirely orthogonal to having or not having backups.

Sometimes you forget or your own storage fails, so having a backup plan is good. Like another commenter said, to me it depends on what the info is. Although I suppose you can't quite "pick and choose" in these matters.

Anyone who realizes that if it ever left your device, it has to be presumed to exist forever.

(You all could reply with your thoughts, as well)