The Honest answer to this is because it is what we were taught, or told, to believe!
Does this make it True simply because someone else, society, or the church taught you it?
As you start to ask questions and put everything to the ‘Logic’ test, you will be amazed at the amount of lies that we are living today!
You must have an open mind in order to do this though!
My suggestion is this:
Start questioning everything you have been taught, then if it actually makes sense, hold onto those logical ideas and simply remove from your mind anything that doesn’t make sense!
This will clear your own mind of conflicts and help you to think much clearer!
This is how you become truly ‘honest with yourself’. Once you have questioned all the ideas you have been raised on, you can then figure out what is true and what is not by simply using a logic test on it. Now that you have started thinking for yourself and become honest with yourself, now you can go out and rather than pointing out how everyone else is wrong in their beliefs, how about helping others to do what you just did. You may not understand this now, but if you teach people how to do this themselves and how to start thinking for themselves, they will be thanking you for the rest of their life, because you have just freed their mind from a prison it has been in for their whole life.