They're a pretty strong brand in their home country of Japan and I guess they'd rather be known as Rakuten worldwide rather than different names in different countries.
Yep, Kobo is now "Rakuten Kobo". I haven't yet seen this on OverDrive, which they also own. To my ear, the names don't go together quite as well, since one sounds very American/English, and the other sounds very non-English (and Americans seem to have difficulty figuring out how to pronounce it).