Why is my sister so worried about her son’s height?

Are most women like that? She said he’s the second shortest in the class and that she worried about her son being short because her husband isn’t very tall (5’9) and she’s 5’3 and that she’s worried he might get his height from our side of the family. But why does it even matter if he’s short?
Why is my sister so worried about her son’s height?
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