Opening doors and other courtesies nobody does anymore

Noticed at the grocery store yesterday that most people just let doors slam in each other's faces. I always open the door for whoever's behind me, man or woman, doesn't matter. It takes half a second and it shows respect. Taught my sons the same thing since they were little. Seems like basic manners are becoming rare. Anyway, if you're not doing these things, start. It's not complicated and the world's better for it.