Reportedly the most common way fire sprinkler systems fail is a closed control valve. Unsupervised control valves are common place. To make matters worse, valves are installed with built-in tamper devices but these devices are often not wired - as shown below. The photo has been edited to protect the inspection company, their tags have been redacted.
Here we have another riser with an unwired butterfly control valve. There is no evidence of a chain lock or seal, either.
Missing signage and electrical supervision (or chain lock or seal):
One alternative to supervision is installing tamper evident seals. In some communities individual serialized seals are required (e.g. State of Florida):