It is the general rule of the system that statuses cannot be deleted. They can only be set to an inactive/deactivated status, which is largely for reporting purposes that may be necessary on past tickets/projects.
You can see a more detailed description of why we do not allow any status to be deleted here: https://solutions.teamdynamix.com/TDClient/Forums/Questions/Details?ID=102703
I hope this clarifies your question about deleting statuses. Please let us know if you have any further questions or if we can be of further assistance in this matter.