I have always liked the PIF idea. I was raised to do such.
I regularly buy meals for servicemen when I see then in the restaurant-I am ex Navy and my DH is ex Air Force. Full cart and a few items-the few go first. I hold doors for all-young, old -doesn't matter. Let traffic go ahead-no brainer.
I lived overseas (Australia) and found that the common manners I was raised with were a matter of custom. I love small towns as the people there seem to still believe in the old customs and in helping others.
In this time of crisis I hope that the spirit of the people of the US reaches out to others and we all remember that we are in this together and a few minutes or dollars of our time may be a life saver to others.
Do unto others as you have them do unto you!