Why 親切 is not usually used when referring to one’s own family or close friends?


"Like 優しい, the na-adjective 親切(しんせつ) means “kind,” and it is used to evaluate
someone who does something kind for a person in trouble or is considerate to
others. However, 親切 is used to describe the character of someone based on
his/her action, and is not usually used when referring to one’s own family or
close friends. "
[source](https://www.japantimes.co.jp/life/2016/05/16/language/two-kind-
complementary-compliments-yasashii-shinsetsu/#.Wu16NnOxU0M)

Why 親切 is incompatible with "describing the character of someone based on
his/her action" when referring to one’s own family or close friends ?

