It's important for Signal groups, because on a new device without a backup the groups you were in don't show up until someone sends a message in the group. Say if you were the only admin in an announcement-only group, no one else can send a message in the group, so that group is now lost to you.

The contact list on a linked desktop client will show all groups you're in, even though your main device doesn't.

On Android, if you know the group's name, you can search in the contact list, and the group will "magically" show up, even though it wasn't in the list.

Not the greatest UX.

This is the only backup feature I’m interested in. I use signal for the expiring chats.