in kansai, people don't usually eat natto. In kanto, they would. For breakfast, it depends if you're traditional or not. At a hotel, it would not be surprising to be served natto for breakfast.
Lots of Japanese like natto, lots of Japanese don't like natto. Go to France and you'll find the same thing is true of blue cheese.
Maybe natto is slightly more popular in Kanto. Maybe it wasn't common in Kansai 100 years ago and that's how the myth started. But let's stop staying Kansai people don't usually eat natto, when it's plain to see that's not the case.