Because it's such a pity if you start off on a bright tone on a story and suddenly realize you are talking about some people having been killed in a road crash.
2015年12月六級真題（第一套）聽力 Section A
I see now it's a huge pity that they rejected your request, but don't lose hope.
2019年12月六級真題（第二套）聽力 Section A
A wise man can live without self-pity.
2019年高考英語天津卷 閱讀理解 閱讀D 選項
They must show each other kindness and pity and the many qualities without which life would be very painful unless one chose to live alone in the desert.
2015年高考英語江蘇卷 閱讀理解 閱讀D 原文
This meant, of course, that he arrived at school early in the morning, dragging his heavy instrument case across the campus to the pitying looks of the non-musicians he had left behind.
2017年高考英語江蘇卷 完形填空 原文
Treat others with kindness and pity.
2015年高考英語江蘇卷 閱讀理解 閱讀D 選項
What a pity! You missed the sightseeing, or we would have had a good time together.