The main reason has to do with 3-D thinking, which is not yet supported by human language.
Picture a tennis ball that part of 3-D reality. We can approximate this 3-D ball, with a large number of 2-D circles, each with a common center; Jesus, but each at different angles, filling in the 3-D volume.
Each denomination is one of the circles, with each having it own unique angle or spin on Christianity. Even though all have different angles, they are all, nevertheless, centered on Jesus. The sum of all these circles approximates the 3-D tennis ball, which is the whole integrated 3-D truth.
Three dimensional or 3-D thinking is not easy to do, since there is no current human language that can support the speed of 3-D thinking. Human Language is more designed for 2-D thinking; cause and affect. To approximate 3-D concepts, it is needs to be done using an approximation in 2-D, so human language can be used.
All the 2-D circles; based on some version of biblical cause and affect, expresses part of the truth. However, it requires all the circles, together, to reach the full truth in 3-D. This extra third thought dimension is felt through intuition and faith, based on focusing, not on your specific angle, but on the common center that all circles sense; Jesus. Atheism which is more 2-D, may not be able to comprehend 3-D thinking and ways to approximate it.
Consider this scenario. Say God used his golden tennis racket to serve this 3-D tennis ball of Christianity. God has a hard serve, causing the ball to distort in 3-D; function of force impulse over time; 4-D thought. It also moves in space and time. The hit would cause many of the 2-D circles, to distort and move out of their 2-D planes, creating local 3-D affects ; inspiration that can add another circle. This 4-D thinking is even harder to describe with 2-D language, but it anticipates the future, such as new denomination circles, with the time element in 4-D, like an inspirational spirit that has a mind of its own; subroutine.
Some day I will discuss thought dimensionality theory which can better explain the levels of human thought. It was a useful tool for mapping out the human psyche with 0-D to 4-D thoughts. In the case of the tennis ball being hit and one inspired to make a new circle this is about 3.5-D thought.
The main reason is there are so many versions of the bible being read by human beings who interpret the version they favour in their own way and nothing to do with tennis at all. Nice apologetics though.
BTW, i spent my working life as a 3D artist and helped develop some of the early 3D software that programs like Maya and 3Ds max are developed from. So i have no difficulty with 3D thinking, what surprises me is that some people think it's special