Assuming that they will eventually have displays around the sides to show ads, they could also use those to show nearby people who they see and how they plan to maneuver around them.
So if they are showing an ad on the display on your side it means that either it doesn’t see you or thinks you are far enough away that it does not have to account for you in its short term planning.
If it sees you and is taking you into account it could show a diagram showing you and what it plans to do.
If they will be running around with displays showing ads I'll never be without few rocks in my pocket just to keep things balanced and maintaining healthier society.
I know it sounds harsh, but force feeding me ads I definitely don't want to see while being unable to avoid them (stay home ain't no argument in civilized world) is unacceptable, and there is no but XYZ to make that stance any weaker.
Ads are a cancer of society, not the worst one but the core principle is rotten beyond reason - manipulate general population at your will, against their default choices, for money or power (or worse).
So if they are showing an ad on the display on your side it means that either it doesn’t see you or thinks you are far enough away that it does not have to account for you in its short term planning.
If it sees you and is taking you into account it could show a diagram showing you and what it plans to do.