How far can the past take you?

Why does it seem that people are so caught up in a person's past that any actions that person takes in the future, no matter how noble and sincere, becomes outweighed by their past actions, however minuscule they may be? Should it be more significant that a person WAS a bad apple before and less so, if not at all, that they have realised their past mistakes and want to change for the good of their future? Why is it that other people concern themselves so much with whether that guy was a horrible drunk or that girl was such a tease and refuse to see that these people CAN change if they want to? It is pathetic to think that a person will always be judged FIRST by their past actions, as though those who judge have never done things that they have regretted themselves. If only people can look beyond their own noses and realises that other people are only human and are also prone to making bad judgements. If only people can realise it is not really the past that matters but what people make of theirs.