A purpose built master clock, will vastly improve your A/D & D/A convertors by eliminating, or majorly suppressing jitter. Jitter, is very subtle distortion caused by your digital-audio equipment not sampling precisely in time. The overall effect of jitter is similar to viewing a video or photo that is pixelated.
Another reason to invest in a master clock for your studio, would be if you have multiple pieces of audio equipment that are connected together digitally. Not having a dedicated master clock can cause pops and clicks due to the equipment being slightly out of synch with each other.