Almost all digital cameras that are released today are color cameras. Several Leica and PhaseOne models are rare exceptions, but these cameras are even more of a niche product than the color cameras or digital backs made by those same companies. Nevertheless, there is demand for BW (Black and White) cameras (for reasons explained in detail below), and many photographers want BW cameras with the same lens mount as their main (color) camera, so that they can use the lenses they already own.
Since a color camera differs from a BW camera due to the existence of color filter array (CFA, Bayer mosaics) over the sensor, converting a color camera to BW is done by removing the CFA*.
After the CFA is removed, the demosaicking process that is done during RAW file processing becomes unnecessary. This, in turn, leads to higher resolution and a decrease in the number of processing artefacts (see the Bayer Moir article), which is, essentially, why people perform the conversions of color cameras to monochrome.