I have learned the hard way but never the right...

I'm assuming you mean when they've done something wrong? It's the same then for when anybody lies or keeps a secret. Why does anybody do those things? It's because they don't want the truth getting out. They're afraid of what you or others will think of them or the way you'll react. In a perfect world, nobody would feel the need to hide anything. Unfortunately, this isn't a perfect world. The guy(s) you were thinking of in this question were obviously terrified what you'd think or say. I agree with jasmia347 about the guys telling you eventually if they really love you.

Guys hide things because they do not want to hurt you. The deepest secret can hurt you the most. Its better to know than not know.

If they really love you they would tell you sometime in life. Maybe now isn't the rite time......