There are exceptions to active fire protection systems because it boils down to two things - occupancy type and cost. Fire protection systems serve two purposes. First, they are installed to put out a fire as quickly as possible based on the occupancy type. For example, an arena that holds 25000 people will have different requirements than a home. Designing the fire protection systems with occupancy types in mind, not only will suppress the fire but also give the occupants time to flee.
Cost is another factor that comes into play with fire protection systems. Fire & Life Safety subject matter experts must take the minimum requirements from the IBC and design the fire protection system accordingly. More often than not, Owners will go above and beyond with their fire protection systems to not only protect the asset but provide the occupants with the necessary tools to be signaled of and escape from a fire.
For example, a data center will require a completely different fire protection system than a three-story office building. For any data center, there are three levels that should be designed - building, room, and rack. The fire protection system in a data center is highly technical in nature and does not use water at all. The main mechanism is gas. This can be a mixture of argon and nitrogen to deplete the oxygen in the data center room thereby extinguishing the fire or can be clean agent gasses that reduce the heat of fire by absorbing it. The cost for this type of system can be as much as 30 to 40 percent of a project's budget.
On the flip side, the three-story office building does not require highly technological fire protection systems. Generally speaking, office buildings require fire signage, fire exits and paths, sprinkler systems, and alarm systems. These systems can be automatic, monitored, or manual. It all depends on the situation. The active fire protection system costs for an office building are substantially lower than a data center. As we can see from these two examples, the design and cost estimation is vastly different.
This brings us to the following point - why doesn't the code just create simple requirements for all spaces? Bottom line is, it cannot because each building situation is unique. What works for a data center will not work for an office building; put simply, the principal firefighting medium is water and this does not work in all situations and all spaces. For example, if a fire breaks out in an attic and it has an active fire protection system, the water will begin to accumulate on the attic floor and eventually break through to the floor below which then causes a new set of problems.
In the end, active fire protection systems cannot be used in all spaces at all times and the code reflects this accordingly.