When we remove the color from a scene, we remove some of the reality. When we remove some of the reality, a picture can (but not always) look more creative and artistic. And, because contrast plays such a very, very important role in black-and-white imaging, a black-and-white picture with strong contrast can look more dramatic than its color version.
There's another aspect to the "why" of black-and-white photography: It's fun!
Today, it's quick and easy to make black-and-white images in your favorite software. Hold your horses! There are some basics that you need to know if you want the most dramatic images, the most important elements being contrast and knowing how digital color filters affect an image. Also important when using software like Lightroom or Photoshop is knowing how far to push the Clarity, Sharpness and Blacks sliders to get an image with impact, without overdoing it.