Why are people so lazy about training there dogs?

I just got back from walking my three dogs. I have spent a long time training them to heel and they all walk with me perfectly. I came upon a couple with a very friendly pit bull that was jumping around and barking trying to get to my dogs. It was a nice dog but the owners were yelling and pulling on the dog trying to get control I asked if they have done any schooling with him and the answer was, "no we just don't have time". If people know there dog misbehaves then why do they do nothing to fix it??? help me understand this please.