I had the same complaint. This NYT article - https://www.nytimes.com/2017/01/09/world/what-in-the-world/avoidance-speech-mother-in-law-languages.html https://w

I had the same complaint. This NYT article - https://www.nytimes.com/2017/01/09/world/what-in-the-world/avoidance-speech-mother-in-law-languages.html https://www.nytimes.com/2017/01/09/world/what-in-the-world/a... - makes a stab at it in the last graf: "Why did the custom of avoidance speech arise? Some experts on its use in Africa and India see it as a way to reinforce the inferior status of daughters-in-law. In Australia, the prohibitions might have been intended to reduce the chance of sexual relations between in-laws." I also wonder if it reduces the marriage appeal for people whose parents' names start with particularly common letters/syllables.