What’s the deal with the lack of awareness in public places?

I know everyone else experiences this too. Every time you are out in public, it could be at the grocery store, gas station, etc. people just do not seem to realize that others exist. People block entire walkways with their carts in one half and standing in the other half. They walk directly into your path. The slowest walkers take up the most space and block anyone with a clue in life from passing. Spend 5 minutes in public and all these things occur. Yesterday, I was getting groceries and a lady came flying with her cart behind me as I was walking to the checkout line. She follows me super closely behind for like 30 feet. Then we get in line, and she parks her cart no more than 6 inches behind me. I turn around and look, then she says “sorry, did I hit you? I was looking all around.” What in the world is the deal? Pay attention to your surroundings. It’s truly not difficult at all.