It would be far easier if there was proof that God existed. Everyone in the world would be forced to follow in Him simply because there would be no way to deny His existence. So theoretically everyone would have what they wanted - everyone would believe in God because everyone would know He was there, and so there would be no sense in disbelieving; and God would have billions of followers.
But with proof comes a lack of choice. The 'belief' part of it disappears, and everyone would be a follower instead. But if everyone all over the world followed, and was convinced by God's everyday presence, perhaps, or maybe the daily miracles that occurred, everyone would become desensitised to His presence. A bit like the presence of motor vehicles nowadays - they are so common you hardly notice them on the roads, yet when they were first produced they were the object of fascination.
With the existence of proof, everyone would be forced to acknowledge God's existence if they wanted to or not - if they didn't, they would be denying the evidence.
But God wants people to choose to believe He exists, rather than forcing everyone to believe. And yes, choosing to believe in something that cannot be proven is rather hard, especially when it's all in a book written more than 2000 years ago. But there are small steps in people's beliefs without them seeing the proof, that happen every day.
I believe that gravity exists. I have been told that it has been proven to exist. But I personally have not seen the proof.
I believe that the air exists, and there are different layers of it way above the Earth. I have seen illustrations of it. I know different elements are in the air. But air isn't visible to me in general, except, for instance, on a windy day. According to the weather forecasts, air in the form of wind moves above the world and brings different weather. But I have seen no more proof than the squiggles on the TV forecast.
Maybe you have heard of Saul of Tarsus. He was a Jew who violently persecuted those who were following Jesus, after Jesus had been put to death. Yet one day he had an encounter with the risen Jesus. This was enough to change him from anti-Jesus to pro-Jesus. Saul of Tarsus is St Paul. You can read about him, and his conversion, here http://www.bbc.co.uk/religion/religi...y/paul_1.shtml
So belief in God isn't so much about being given proof as to looking for it. From my own studies I have found that the interior of cells is miraculous, and it is hard to believe that such a refined thing arose purely from evolution. But that isn't definitive proof that God exists. You have to take a step, find out about Jesus and try to see things objectively rather than sceptically. You have to search honestly for God. God revealing himself to sceptics would be far too easy. God will know the disbelief in your heart and it's a kind of veil that keeps you apart.
I have myself only really begun my Christian journey and so I am going off belief alone. Yet people here further on in their Christian walk have had proof to themselves that He exists. Try reading people's testimonies in the testimony forum: they can be food for thought.