It‘s even better: it has a free US phone number. So my insurance could call me on that number while I‘m in Japan.
Recently this has been unified throughout Europe, including removing roaming charges for data, but calling from/to outside Europe is still very expensive. Even sending text messages (and receiving, which is normally free) is expensive. Thus Skype. And it's also cool to have a Skype-in number in Japan[1], which will be forwarded to your Skype account wherever you are, or to your phone if you're offline (if so configured). That's nice when you have very old family members who prefer to use a (local) phone call to get in touch. So Skype covers some use cases which I can't easily cover by other means. For the "normal" communication which doesn't involve a phone I mostly use other tools nowadays though.
[1]With the restriction that Japan only allows Skype-in numbers if you're a resident.
For ordinary chats, groups, video conversations, file / movie / photo / album sharing etc. I use Naver Line, as nearly every Japanese do as far as I can tell.