I once had my car break down on a busy freeway and since I had to wait for the repair service to come pick it up, ......It Didn't take long for the police to show up to question me what I was doing there either, so I guess the police just looks for unusual behaviour.
I think the police stopping by when your car breaks down is a good thing. 
Having worked for a Highway Patrol department in one state I'll tell you it's more than a "good thing."
Interstate highways (freeways in general) exist to move vehicles. Anytime a vehicle or pedestrian or dog, ladder, mattress, etc. is stopped anywhere on the highway, it is unsafe. At the very least, it's a distraction to drivers. At worst, it's an obstacle. With the prevalence of cell phones the last 20 years, every such instance floods a dispatch center with calls so everything is known. Officers are dispatched. Depending on where/what it is, they don't give it a high priority, but they'll eventually investigate. It's also gender specific. If a woman is reported to be sitting in a car on the side of a road, that's a higher priority than a man -- from days of yore when chivalry ruled, I suppose. Nevertheless, it's a reality.
These days I'm guessing if you stop on the shoulder AND get out and start taking pictures, officers will get there faster!
