To me, you'd have to ask the question, "what causes people to believe?"
Injustice, powerless, and impoverishment... (people feel that after they die, there will be a better life awaiting them where such things as impoverishment, powerlessness, and injustice don't exist).
Universe seems too intricate... (usually belief that because of 'x' and 'y', there must be some hand at play).
Parents believed... (what causes many other people to believe, and if you tie in some of the other reasons it merely goes to polarize their views).
There are other reasons but those I tend to see as the most common of reasons.
So, will it ever lose its grip among people? I don't know, I believe people will justify their faith in many ways and find an alternative route to justify their faith around new evidence about the universe just as they do so now. Their faith acts as more of an illusory life-vest.
If I have money in my wallet/bank account and am walking outside, I have no worries about finding my next meal, when I'll eat, and the like, I feel sort of protected in that regard and really don't need to worry about it because I can simply provide it for myself. People generally believe in a god in the same sense, that no matter what the situation they are being protected and provided for. More often times than not, they are not provided for and they attribute this to a learning curve, punishment, or some other ill, and when something good happens, then that was their god rewarding them for some good. This just adds more webs of polarizing viewpoints and clouds their reasoning. It hurts more than it helps because they fail to see what was it of their own doing that caused a 'good' within their life. Had more energy throughout the day? What did you do previously, like what did you eat, what was your thought-life like, did you pray longer than usual (prayer is more like meditation and can be useful in terms of meditating; it is bitter-sweet)?
Is the Bible a guidance for humanity?
I do like some books from the bible though, but do I think of it as a guidance for humanity? No, I do not.
Would the world be a better place if we were all evangelized?
Hm, basically if everyone were apart of the same religion and followed the same customs, practices, etc...? Not really. Of course when you think about it on the surface it could be reasoned that, yes, it would limit suffering, but that 'faith' is established on ignorance. I remember reading that when disease and death entered the area and was starting to kill the citizens off, some people were labeled 'heretics' even though they did nothing of the sort to establish themselves as heretics so they and the children were killed. The world being a better place (in terms of humanity) is dependent on what we ground our code of what we live by in, if we live by a code of ethics in the belief of a deity, that won't lead us to a better world for ourselves and will hurt us more than it helps.
We can make our lives better by establishing a code of ethics and regulation for humanity, but I feel that has a long way to go as many parts of the world reject such an idea of doing away with religion.
Does anything else teach better ethics than religion?
Yes, like some people have stated, 'secular ethics'. It grounds its principles based on the act of reasoning and not deriving the ethics from a sketchy way of seeing things. To me it is more objective for rational beings than it is subjective like religion-based ethics.