I've rarely seen spot lamps on commercial tractor (the truck part)/trailer combinations. I'm talking of cab mounted spot lamps controlled and aimed by the driver. Now, on the other hand, commercial trucks have to make deliveries in all kinds of weather (it has to go through!) and many have foglamps or auxiliary driving lights mainly mounted to the front end/bumper. Another consideration is that, while a first world country, many trucks have to traverse narrow secondary roads and some have lights mounted so that the driver can see where the edge of the roadway is located. Legally, at least in California, only two sets (a total of 4) of forward facing lights are allowed to be on at the same time. High beam lights are considered to meet that 4 lamp limit. So the truck can have one set of low beams lamps and one set of auxiliary lamps in use. Plus there are often lamps mounted to the rear of the cab to keep track of what's happening to the trailer but they have to be carefully aimed so that they don't blind drivers overtaking from the rear.
I'd never heard the term SAR before so I had to look it up. "The term SAR was derived from the American Kenworth item listing: Short [Bonnet], Australian, Right hand drive." We don't come upon Kenworth SAR's in the wilds of California. https://www.pressreader.com/australia/big-rigs/20160812/281728383905672