Because to believe the Buddha was talking figuratively, not literally when he talked at length, over and over about rebirth, other realms, conversation with devas etc etc, you would really have to be twisting around his words from what they plainly say, The Buddha wasn't a secular Buddhist, quite the opposite, why can't you just man up to you disagree with the Buddha, instead of trying to put your modern ideas in his mouth.......and try and make your ideas fit with his.
18 years ago I made one of the most important decisions of my life and entered a local Cambodian Buddhist Temple as a temple boy and, for only 3 weeks, an actual Therevada Buddhist monk. I am not a scholar, great meditator, or authority on Buddhism, but Buddhism is something I love from the Bottom of my heart. It has taught me sobriety, morality, peace, and very importantly that my suffering is optional, and doesn't have to run my life. I hope to give back what little I can to the Buddhist community, sincerely former monk Johnhttp://trickleupeconomictheory.blogspot.com/