Why not leave a dirty diaper while you're at it?

Yesterday on the bus from the plane to the terminal at Frankfurt Airport, I was standing near a woman who was carrying a baby in one of those Baby Bjorn contraptions that is like a reverse backpack where the baby is carried in front facing forward. Well, as we neared the terminal, all of a sudden the baby basically projectile vomited all over the floor (thankfully, she was facing the opposite direction from me). Now maybe I'm being insensitive because I don't have kids, and it was only baby puke, but in that situation, shouldn't the mother try to do something to see that it's cleaned up? I can understand she couldn't clean it because she had the baby, but she had family with her--would it be too much to ask for them to try to clean it up? (People were handing them kleenex.) Or at least to let the driver know on the way out that someone should probably come and clean it up? Nope--we got to the terminal where we all had to dodge it on our way out and they all just walked right into the terminal without telling a soul. I feel bad for whoever got on after that--it could be like the first weekend Gretchen and I spent together in New York and a packed subway pulled up with one car much more empty than others, so we got on and realised it was empty because someone had hurled right there in the middle of the car and everyone was squeezed into both ends of the car to get as far away from it as possible, and at every stop you could see people get on the car and watch their faces shift from happiness to horror as they realised what they were encountering. Yeah, kinda like that...