To permanently decannulate a patient, you need a doctor's order. Protocols by either nursing or RT will dictate the weaning process and parameters up to that point.
In some facilities, such as subacutes, the RNs do the routine and emergent trach changes if RT is not present.
Decannulation can also change the qualifying status of a patient in that facility and a transfer to another unit may need to have been ordered the physician to be initiated. Thus, everybody needs to be on the page in the care plan and progression of the patient. It may not be a "lazy doctor" but rather the wheels of healthcare and the stipulations for levels of care that can determine decannulation.