Another factor is the 'age' of the structure. Open bulb, incandescent fixtures (like porcelains) are still in an awful lot of 'closets' around here. Offhand I don't know when 'closed' fixtures were added.
As to CCO inspections, I will inquire to the CCO inspector, and the Uniform Fire Dept Insp., if either of them check 'closet lights'...which I doubt.
The NEC is not retroactive, nor is every electrical installation/modification permitte and inspected.
That all said this situation was still a tragic loss of lives.
