Most major biological molecules, including all proteins, DNA and RNA, point in one direction or another. In other words, they are chiral, or handed. Like how your left glove fits only your left hand and your right glove your right hand, chiral molecules can interact only with other molecules of compatible handedness.
I read about it a while ago. Apparently, right-chiradial proteins can’t produce some molecules the left ones can or react entirely different. I guess lc was just more practical?