Grocery Gripes

So I had the privilege of going to the grocery store with just one kiddo. And I only had a small list so it should have been a fairly pleasant experience. Needless to say it wasn't. All because of one person. It amazes me that one person can literally ruin your day or at least your shopping. So FC is really a sweet little girl but Mommy decided against all rational thought to take her to the grocery store right during nap time. We hit the produce first and as I'm putting the peach in the bag Funky grabs it right out of my hand. I thought she wanted to help so there I am trying to teach her "in" and put it in the bag. She gave me a funny look and then preceded to try to take a huge bite out of the peach. Oh, so you're hungry. Okay, so off to the bakery section I go to grab a bagel. I know real nutritious. I wasn't prepared with a snack because my Cheerio stash was never refilled and she had just eaten lunch. Anyway, the bagel worked since she's teething so we were back on track. Admittedly, I was keeping one eye on her to watch for choking and with the other I was looking down the next aisle to see if I needed to go down it. Well, this woman comes bounding around the corner (one with a huge display), and I crash right into her. Now I fully realize that in all likelihood I was at fault. So I said "Sorry" not once but three times. The woman did not say one word. She rubbed her leg and just glared at me. She looked at me like she had just caught me in bed with her husband. I was on edge the rest of the trip.
Maybe that's why I also have this question for any of you who may know the answer. Why do people put their babies in slings, Bjorns, etc. to go grocery shopping? I mean you have the ability to use your floppy seat on the cart. So why lug the kid? Now I have noticed that the women I see doing this are typically the skinny b*&*%s that probably have super cores and no back problems. I just still don't get it.