This is Why You See Doggie Doo Bags on Windows in Portland, Maine
Before everyone automatically assumes that I'm an idiot, for not immediately knowing this, know two things about me: 1. I have a cat that poops in a box and 2. I lived the vast majority of my life in rural Maine so dogs would just do their business in the fields/woods.
It was actually months ago that I first spotted a purple baggie stuck to the back windshield wiper of a car in Portland. I actually almost stopped to take a picture because my mind immediately went to, "HA! Who did that guy tick off?" Perhaps that's more of a commentary on how I view humanity these days.
Recently I was FaceTiming with a dog owner friend of mine and she casually grabbed a poop bag off the back of her car. I couldn't believe it! This is a part of dog-owner culture that I have not been privy to and had to ask.
Her answer immediately made me think, "Oh, duh. That should have been painfully obvious because that makes all the sense in the world."
Dog owners do this because who the heck wants to drive around with a stinky bag of poo in their car? Certainly not I. It's bad enough I have a box of poo in my living room thanks to my cat's litter box. And sometimes out of sight out of mind sticks and the bag may stay there overnight.
So, mystery solved. It's simply a life hack to not have your car cabin smell like dog poo.