I think those people who break up the relationship without saying a word are just scared. It can be by any reason: they don't want to hurt your feelings or don't want to put themselves in an awkward position...But in the reality they just don't respect the person they break up with. I hate when the person just can't give me a clear answer if something went wrong. If it's over then it's over, but you must tell about it. Everybody deserves to know the truth no matter how hurtful it can be.