Why is it that people prefer to believe years long traditions about the state of the dead?

I was talking with a friend of mine who says that her dead husband has been visting her lately and telling her how to get promoted at her job and other things that she had been struggling with. I showed her all the Bible verses that say that the dead are dead, they know nothing, nor can they come back and visit what is vistiting her is nothing but the devil or one of his agents to fool her and play on her weaknesses. But, she says she doesn't believe in the devil, but she believe in what she can see and hear and feel. I tried telling her that actually what satan is counting on; but still she won't stop talking to that creature that visits her. I thought about coming over and staying for a while and see if it will show up while I'm there, then ask it in the name of Jesus Christ to leave and never come back; but if she not willing to let go, it will only come back after I'm gone. But, there are so many people who will be trapped in this, like those who say they call the hotlines, just for fun; but the Bible speaks against such acts. So, if we are suppose to be Christian why do we presist in doing things that the Bible clearly tells us not do?