Mo Yung F'uk was so singlemindedly focused on the goal of restoring the Yin Kingdom that he had no time or attention for anything else, especially not romance. Therefore, it's not surprising that he took no personal interest in either Ah Chu or Ah Bik. After all, they were merely assistants to his goal.
Still, his utter disregard for Ah Chu seems a bit surprising. Even if he had no personal feelings towards her, it's odd that he didn't seem to care or even be aware of the fact that one of his two assistants went *missing*. Ah Chu not only left Mo Yung F'uk's service, but became intimate with Mo Yung F'uk's rival and potential foe Kiu Fung, and then died. I don't remember Mo Yung F'uk even casually asking or wondering once what happened to Ah Chu. He completely disregarded her; it's as if she didn't exist.
We also never saw any "screentime" between Mo Yung F'uk and Ah Chu together (and barely any with Mo Yung F'uk and Ah Bik either), so we don't really know what their working relationship was like. Ah Chu and Ah Bik were both pretty loyal to their employer, but I don't think he reciprocated with any appreciation for either of them.