Electrical work is to be performed in a de-energized state unless energized work can be justified. Where energized work is permitted without justification, the company or organization can be subject to being fined for willful violations, which are the most expensive types of fines. They can also be subject to possible criminal charges where someone gets seriously hurt or killed.
The energized electrical work permit is also a good document for documenting the required shock and arc flash risk assessments that are required whenever the is the possibility of harm from electrical hazards.
The procedure is in place to protect the owner and the worker. Here is a great article on the importance of following the rules: