A work can have many Alternate Continuities.
The reasons for doing so are:
- Same characters, but different setting and timeline.
- Experimentation outside of canon, creating a new, separate canon without needing to do a Continuity Reboot
- Fan Fiction purposes, but then again, as Alternate Universe Fic states, all Fan Fic is arguably Alternate Continuity.
In the case of a franchise, Sonic the Hedgehog is a massive Cash-Cow Franchise which can justify why there are fifteen Alternate Continuities.
