I think moving sidewalks could be more suitable for shorter distances than public transport or taxis. In many situations, it doesn’t make sense to order a taxi for a trip of less than 1,000 meters, or to walk to the nearest bus stop, then wait for the bus, just to travel a single stop. There are many people with disabilities who may struggle to walk these distances and would benefit from such an option. Additionally, moving sidewalks could reduce the time it takes to travel short distances within cities.
The problem is cost/benefit. most places just don't have enough people walking far to make them worth it. They cost a fair amount to install/run, and so when few people use them they are not worth it. They also block people who are trying to cross the street (to get to the next store) instead of going down the street. They they are common in airports rare elsewhere - they don't make sense for most locations.