People ride scooters all over the place in Japanese cities. They're pretty commonly used for delivery services as well. Biking culture is actually more aggressive than in many places in the US. For example, it's for some reason acceptable to ride your bike on crowded sidewalks, belying everything I understand about notions of Japanese civility.
Not really my experience. I've seen people trying to ride bikes in areas where people could barely walk. And I've been on many sidewalks where not watching your six when moving right or left was an invitation to get run over on a sidewalk.
Electric bikes are making headway but many employers have rules specifically forbidding employees from riding them (or any other form of personal transportation) to work. There is a major national insurance company with which employers have a contract and that company won't pay out for accidents that happen on the way to or from work while the employee is on a bicycle or in their own car, so employers ban commuting by bicycle or car.