This is interesting.
All points mentioned so far are great, if somebody who's into form and geometry, BW would naturally be his choice.
And sometimes colour can really be distracting as well.
Or simply because that it's easier to develop your own BW negatives.
Here's my two cents' worth -
If you think about it, photography hasn't been around for that long.
And colour photography, even lesser.
To be exact, the first successful color process was introduced by the Lumière brothers in 1907.
Kodachrome, the first modern color film came about only in 1935.
So since the camera obscura in 1826 until 1935, what people associate photography with is the black and white image.
As such, even in modern times, BW photography inspire within people a sense of 'history' and 'authenticity'.
Simply because they associate it with the origins of photography -
or what they perceive, consciously or subconsciously, true or 'pure' photography.
It just appears and appeals to them as being more stately and regal.
And it so happens that the by-line of Leica, or film photography is -
you guessed it - history, heritage, purity, analogue, authenticity.
The list goes on.