Electrical equipment once installed requires maintenance whether is operational or not.

The primary reason is to ensure the electrical path through the equipment is functional, conductive and operating as intended.

Secondly, the mechanical functions must also be maintained in a fully operational manner to  ensure safe operation when required.

Rule 2-300-1,2 of the Canadian Electrical Code (CEC) requires functionality and operation be maintained throughout the life of the equipment.

This is not just in reference to front end equipment and devices, but also the equipment hidden from view in an out of the way room elsewhere.

Excerpt from the Canadian Electrical Code:

MAINTENANCE AND OPERATION
2-300 General Requirements for maintenance and operation
1) All operating electrical equipment shall be kept in safe and proper working condition.
2) Electrical equipment maintained for emergency service shall be periodically inspected and tested as necessary to ensure its fitness for service.

Equipment stakeholders must be cognisant of consequences of dysfunction of and a path to reliable function.

Equipment that is not maintained when required to operate can fail partially or completely.  This can cause arc flashes, brown-outs, fire, explosions, system failures and damages, etc.  These conditions can be prevented or considerably reduced by performing preventable maintenance such as:
1. Equipment exercise
2. Infrared surveys
3. Conductivity tests
4. Operational testing

As seen recently in the media, the consequence of failed equipment bonding resulted in the electrocution of twelve young children at a water park.  If the bonding system for the railings had a conductivity test performed as part of a scheduled routine maintenance, this consequence could have been prevented.

See the link to a new voluntary standard put forth the CSA Z463 which is getting momentum to becoming mandatory and consistent with CEC Rule 2-300-1,2.