They were actually quite common since spreadsheets, word processing etc. generally didn't need colour (and the extra cost) but benefitted from the higher resolution. They were also usually 'real' gray scale, i.e. white or paper-white.As well as VGA-compatible monochrome monitors.
At one time, I owned a couple of the Tatung 14-inchers, but, as VGA-using programs began to make increasing use of color (with no way to force a "mono" rendition), they became pretty much useless.