Believe it or not, Windows Phone 7 had that in 2010-2011, right into the OS itself. They integrated it on a per-contact level too, you just clicked on say Craig and had a drop-down to switch which service to message Craig on, but it was a single message history that integrated all the services. It was a damn good mobile OS, way ahead of the curve, easy on resources, slick animations, had UI/UX consistency, accessibility like putting all menus at the bottom of the screen so you can reach them with your thumb, including the damn browser address bar (which only now made it to Edge). But of course, being Microsoft, they fudged it horribly and it died a slow painful death while the head of Windows Phone kept denying it was dead like a damn cult leader.