Natural birth almost by definition cannot happen in a hospital. You need to feel safe, and how to feel safe in a building full of strange people, unknown voices and smells? You need to be in tune with your body and it is difficult to hear, let alone to follow that quiet internal voice of your instincts during frequent interruptions and instructions from the staff.
One of the greatest advantages of a home birth is that you are on your grounds. You feel stronger, your birth partner feels stronger, you both have a say. Your wishes are more likely to be respected. Even if you have a strong personality, while being in labour you feel rather like a fragile girl, not like a warrior.
Hospital is an unfamiliar ground and once you arrive, you automatically get into an outsider role, while the doctors or midwifes automatically get in the role of locals, the experts. Even with lots of good will on the staff side, it is automatic - they say, you obey. At home, you are the mistress and everybody can feel it. Home is your place, your strength is there. Your castle, your rules.