So after 3 years of asking everyone who I saw not cleaning behind their dogs I have the following statistic:
* 100% are white male above 50
* 100% knew that their dog did this
* 100% didn't care at all
* I saw a couple of them doing this repeatedly
Male above 50 should not be allowed to own a dog. Or at least need to have a public visible ID attached to them on their bag (not on the dog).