>Monotheism has less gods, and it helps us unite.
That's exactly the reason.
Thousands of years ago, all religions started out the same way - veneration of elders and personification of natural events.
The gods were separate from mankind; they had their own views and ambitions, and fate itself didn't care about individual men.
Structurally, the old religions were about the mutual relationship between nature and man, a byproduct of our veneration and validation for others.
Structurally, Christianity is unlike the old religions, because rather than venerate and validate others, we're taught to worship an almighty God and put his ambitions before others or our own.
The reason we don't talk of "Honour" these days, is because nobody knows what it is. They have no need for honour, because their personal god validates who they are; and they become more schizophrenic in that sense, because that leads them to be even more religious. I digress; religion is the byproduct of the society. We've abandoned honour for materialism, because materialism gives us a sense of worth in a Jewish capitalist society; and because of this, we're taught that progress is the ultimate goal, because progress gets us "Closer", and we associate closeness with validation. The materials of progress are charged with the validating qualities of popularity, vanity, and power.
Who needs honour, when you can have the first new iphone and become the talk of the town?
Christianity is a byproduct of materialistic thinking, giving us a god who punishes and rewards, one who gives us personal validation if we eat crackers and spoiled grape juice.
A modern atheist, as a result, isn't a true atheist, because his religion is the same religion as Christianity; he believes in the personally validating qualities of his material god, the rituals of consumerism and rebellion in the scripture of globalist capitalism and marxism.