Self-dispatching or self-deploying resources may interfere with incident management and place an extra logistical and management burden on an already stressed Incident Command organization.
If your incident uses a self-dispatched resource, it is possible that your agency or jurisdiction may become liable for their actions, for any accidents or injuries they incur while working, and possibly expenses and reimbursements.
Although these resources may be trained and capable, the risks associated with assigning unrequested resources may outweigh the advantages.