Arianespace does that with their Ariane V, but it comes with organizational headaches, because you need two payloads of appropriate mass, that are ready at the

Arianespace does that with their Ariane V, but it comes with organizational headaches, because you need two payloads of appropriate mass, that are ready at the same time, and that go into the same orbital plane. If one payload is delayed (happens often enough), you can't shuffle the other one around on short notice.