Monday Mystery

My friends and I have "Movie Monday" just about every week. We usually combine it with lunch. Last week, when I was walking to Panera Bread, I came upon this door on the rear of the restaurant. 

What the heck is a "sprinkler riser room?" I cannot imagine.

So, I decided to look it up. Here is the long answer:

A sprinkler riser room is a designated area in a building that houses the main components of a fire sprinkler system, including valves, gauges, and alarms. It provides a central location for the system's control and maintenance, often found on the lowest level or near an external wall for easy access by emergency personnel.

Okay, I get it. But what exactly does the name mean. I get the "sprinkler" part and the "room" part. Why is the word "riser" even in this sign? Would there be some confusion as to where the sprinkler works were if the sign just said "Sprinkler Room?" Me thinks not.

It's still a mystery to me!