IIRC, both generation Gates belts require high tension to keep belt tracking properly. High belt tension consumes a significant amount of the pedaling power. Std chain drive is easier, more efficient and cheaper.

Belt drive would be more common if it didn't require the ~$1000 cost escalation of a Rohloff Speedhub (and the three Gates components) for adequate loaded touring gear range. There are cheaper IGHs (Alfine/Nexus) but they are less robust with lower gear range. Additionally, belt drive requires a bike frame with some provision for belt tension adjustment, i.e. eccentric BB or swinging/sliding dropouts:

https://www.youtube.com/watch?v=b6ZKqy2zKsA