Some occupations involve plenty of walking. Think of construction workers, production floor managers, janitors, stock clerks, mechanics, tour guides, etc.
It's possible to exceed 10,000 steps at work. Assuming 100 steps per minute, that's over 100 minutes of walking. Running cadence is nearly double that. It looks like the equivalent of over 4 hours of running (8 hours of walking) if the person works five days a week. Four hours of running at 10 km/h would be 40 km. If the person bikes to work, there would be even more easy mileage. Recovery and injury prevention are important too.
For a person who's training for a race, should they be focusing on interval training since the job and possibly commute already has plenty of easy mileage?
Updates It's known that people tend to do their easy days too hard because actually running easy feels too easy to be beneficial or a good workout. Those who do polarized training spend around 90% of their exercise time at an easy pace. My understanding is that the walking at work also counts as recovery exercise.
Maybe one argument is that 10,000 steps spread out all day has a different effect compared to having it done all in one go.