when someone cheats why they blame someone else?

Because they want to be forgiven and they will say anything. It was their choice and they are to blame. It's strange how the person who is cheating gets forgiven but the person they were cheating with doesn't. Once you cheat, you're always going to cheat. And women who sleep with married men and say they didn't do anything wrong are scum too.

For some it's easier to blame others than to accept responsibility

It's called denial mixed in with enough guilt to make that cheater act totally irrational and in his own best interests.

its the devil made me do it excuse..blame him, not me..

Because theyre cowards.