Nice story. Only think I think they are missing out on are the tablets. We (social circle) use hangouts more and more, because it's available to the few that use dumb phones in combination with an iPad.
Sure I would kill for an ipad or a desktop version but does iMessage work when your friend uses Android or Windows? What about Grandpa using an old Nokia? How about those old friends who moved away to another country? Moving from the US to another country isn't very common, but it's fairly common for the rest of the world - born in Dubai, Schooled at Cairo, works in France is very likely.