No Excuses

Why is it that whenever another person on the street and I almost bump into each other, or actually do collide (yes, it happens), I’m always the only one who says, “Excuse me”? Can someone please explain that to me? I’d really appreciate it, because I’ve just about had it with people’s lack of even the most common of courtesies.
About 15 minutes ago, as I rounded the final corner (what is this, a horse race?) on my walk home from the gym, a UPS deliveryman rounded it in the opposite direction. “Oooh! Excuse me,” I said, even adding a bonus tiny smile. He said nothing. Didn’t even blink an eye. No acknowledgment whatsofuckingever.
In addition, there have been so/too many occasions where I’ve held the door open for other people — sometimes an entire fucking parade, it seems — as they’ve passed through it in the opposite direction, and not one of them has thanked me. What, am I their personal butler/doorman/doormat? You’d better believe that as each successive jackass passes by me, I offer him or her either a heartfelt “Excuse you” or “You’re so welcome”. Still, rarely has someone acknowledged that I even said something.
I am not invisible. I may be a mere slip of a girl, but the last time I looked, I was still visible to the naked or not-so-naked eye. When I peer into a mirror, there is indeed a reflection — contrary to what some people may have said about my being a “vampire” (given my aversion to sunlight and daytime and the fact that I have a black cape permanently affixed to my shoulders). But when people don’t make the extraordinary effort to acknowledge that they are not the only creatures occupying the planet, I really want to relieve them of some of their blood.