iMessage doesn’t need to be “exciting”. As a built-in experience, iMessage needs to be a seamless replacement for SMS. Its boringness is its brilliance. For most users, it subjugates SMS without them even realising it is happening. You get the benefits of iMessage (read receipts, free picture messaging, group messaging) by doing absolutely no work. That’s the beauty of it. Users wanting novelty features, like Snapchat’s ephemerality, can go to the App Store.