If I choose to stay home as much as possible then I am reducing the possibility of infecting another person. If I choose to leave my house and happen to unknowingly be masquerading as a walking petri dish of COVID19, then I am putting others at risk.
When I get to close to someone and clear my throat, exhale deeply, I could be leaving the virus lingering in the air. If I cough or sneeze and forget to do it inside my elbow or a tissue, that virus can hang in the air for a couple of hours and someone can walk through that space I just walked past later on and breathe it in. When I open a door, pick up merchandise from a shelf and put it back, inspect a piece of fruit at the grocery store and put it back, place my hands on any surface that another person may also place their hands, I could be leaving the virus behind. When someone else touches that surface and then touches their face, I have infected them and anyone they come into contact with. What if that unknown person is over 60, asthmatic like me, has high blood pressure, heart disease, diabetes, has cancer or lives with someone who does? By leaving my house, I increase the possibility that I unknowingly just killed someone. I can't control what others will or won't do. I can only control my own actions. Everyday that I don't eave my house, I can go to bed knowing that I did not play a part in someone else coming down with COVID19 and dying.
This is why I stay home as much as possible. I hope this helps