Besides those two reasons above, it is also a 'testing ground' for new features in Activiti.
It is meant as a showcase of how Activiti could be used. We have some manual testing going on each release, but nothing compared to what it would be if this was something that has real customers. That being said, it is of course possible that it fits your use case perfectly. If so, nothing against using it in production. Just bear in mind it was never tested/designed that way.