A certification is as good as the manufacturer's quality control program on a given day. In the past, each worker has had a relationship with his tools. In many cases, the apprentice's first job was to build his tool box, then his ladder. For hundreds of years, workers made their own ladders and kept them repaired. Many lasted generations.
Modern ladders are mass-produced items with specifications limiting how they can be used.
New laws and consensus standards apply to the exposing employer, and to the controlling employer on each work site. Employers have greater responsibilities. Among those, is the duty to inspect the job site where your employees will work. You are required to assess fall hazards and create ways to prevent falls. A competent, trained person is required to provide your training.