Writing on the wall

On the way to work today, before the subway a lady and her husband left there house (they didn't really seem like they were together but when you've been with someone that long maybe you don't hold hands any more) the husband started picking up the rubbish off the floor and then he pointed out this on tiles of the subways that wasn't there before, he seemed quite upset about this. It seemed really nice that he cared so much. I looked at the rubbish on the way home but I couldn't bring my self to pick it up as it just seems really dirty, I feel a bit bad about this.