Why do guys do this? Help Me guys tell me why!!!!!?

Why do guys get girls hopes up?!?! They say I love you, your beautiful, I will never leave you, or do anything stupid to lose you. And then they Frickin cheat on you with another girl or an ex girlfriend, and then leave you for that girl or ex girlfriend. I am just so tired of it! There is no reason for guys to do that sure they may not want to hurt the girl, but why say it in the first place, and they lie when you cheated, honesty is the best policy, ya you guys may be scared, but us girls deserve the truth, it hurts when we find out other wise, and why do the exsessive cheaters keep cheating and don't care how many hearts they break?