People absolutely do care what strangers are doing
People always say nobody cares about you and everyone is too busy thinking about themselves. I do not buy that at all.
Try doing one thing that looks even a little unusual in public and you will feel it immediately. People stare, people judge, people make faces. They might not say anything out loud, but they definitely notice.
I used a sun umbrella outside once and got looked at like I was doing something insane. That was enough to kill the whole nobody cares myth for me.
3