Why do surveillance cameras face oncoming traffic at every intersection?

It would appear that the answer was in the description you offered in the question. I have to assume a rather youthful age. I have to assume that there is a texting addiction that commands, in the brain, to reach for the smartphone each time VERSUS analyzing the situation and given it some time and effort as to resolving it. A quick reference to the dictionary as to the term :"surveillance" would have yielded the guidance required to arrive at the proper conclusion. In the now classic puzzle, not a joke, it has been asked that if a plane crashed in international waters, where do the survivors get buried? Give yourself some time on this one. In the movie, "The Italian Job," there are many scenes as to the traffic control center in Los Angeles with traffic flow and congestion being monitored. Surveillance cameras also are used for crime prevention. In the Bourne movies these are shown and used to locate people. Surveillance. A French term. Look it up. As to why are you noticing these cameras, probably another posting is required.

Actually there are both front and rear traffic cameras posted at many intersections throughout the country. The front view cameras are simply more visible when you are driving.

Because they are traffic cams not surveillance cameras. There just interested in traffic flow not what your license number says.