Many people use monochrome to "fix" a bad photo. Others seem to have doubts about which version they prefer, so they post both: color and black and white.
While you can get good results every once in a while, this approach is wrong.
The tools you have available in black and white photography are very different from the ones you can use when shooting in color. The image should be in your mind first, then -and only then- we can choose whatever tools we need to create it.