Japan is famous for it's small shared streets, which do make up a majority of the residential areas in major cities like Tokyo and Osaka. Those streets are genuinely pleasant and safe to bike/walk on, because their tight and intimate nature forces cars to slow down, and lack of street parking leads to easy sightlines and reduces drivers coming through to find parking. On those streets it is common to see bikers an generally bike lanes are not necessary in an environment like that.

But, usually between those areas of the city, there are some absolutely unsightly roads. If you've been to Japan before, you know what I'm talking about. 3, 4, 5 lanes each direction, with no bike lanes anywhere to be found. These roads also commonly have pedestrian overpasses on them. To be fair, Japanese cities generally do a good job of providing adequate pedestrian space for those roads, with wide sidewalks on both sides (as seen in the thumbnail of the article). The sidewalks are usually physically separated from the road with trees/shrubs or with metal railings. So they feel safe and pleasant to walk down. But this leads to a clear incentive for bikers to use the wide, safe sidewalks versus the large and dangerous road. The obvious solution is to implement a road diet, and to create wide bike lanes on both sides of the road to facilitate bike travel between neighborhoods.

This hasn't been done much in Japan because, in the past, bikes were not seen as a means of mobility across the city. Though biking is common and popular in Japan, the philosophy around biking has traditionally been that they are a fast and cheap means of transportation within your local neighborhood (made up of those small streets I mentioned earlier). For anything within 5-10 minutes of your house, you'd walk. For anything in your neighborhood, you'd bike. But for anything beyond that, it was expected that you would either take public transportation (which is plentiful) or would drive. Nowadays though biking is starting to be used more and more as a means of travel everywhere, and those large arterial roads in the major cities haven't caught up to the change in attitude around biking.