If I have DayOne and this site why have both?

It has been a while since DayOne was acquired by Automattic, the owners of WordPress. By now I was expecting some kind of tight integration between DayOne and WordPress. However, it makes me wonder what is the point of having both? Obviously one is very much public (a wordpress site), and DayOne is the exact opposite. Perhaps that is the essence of the problem though, perhaps that is why there has been no news on some kind of clever integration. I doubt it though.

It leaves me stuck with this question. Why have both?