> I am failing to see the additional value of combining them. If Google bought WhatsApp and combined it with the stock SMS app of Android, I don't think I would prefer that.
Well, it's not useful now, but imagine in the 00s when a minority of users had iPhones. Having two clients, one for SMS and one for iMessages, would have gone against the simplicity Apple was aiming for with respect to user experience. Combining it meant that users could get a better experience (than SMS/MMS at least) when communicating with other iMessage peoples, but not have to swap out clients to chat with others.
Well, it's not useful now, but imagine in the 00s when a minority of users had iPhones. Having two clients, one for SMS and one for iMessages, would have gone against the simplicity Apple was aiming for with respect to user experience. Combining it meant that users could get a better experience (than SMS/MMS at least) when communicating with other iMessage peoples, but not have to swap out clients to chat with others.