I will answer that with quite a bit of speculation on my part, but I think some jurisdictions have not followed the route of Nova Scotia because they don't think that's the ideal approach to take. Some groups will say that mandatory reporting is the best route to take: put a positive obligation on everyone to report. It requires a robust infrastructure to respond to that reporting.
A lot of people would say that mandatory reporting is not the ideal response, that the ideal response is to provide resources and support to the older person who is a victim or in danger, and reporting doesn't necessarily result in any of those things going to the older person. Mandatory reporting can sometimes only amount to things like breach of privacy and a lot of intrusion on the older person's life. That's a lot of sound and fury signifying nothing in terms of positive impact.