To say that somebody does something alone means they do it not in the presence of others.

就是说人孤独而死的意思是,他们死的时候身边没有别人的存在。

耶鲁公开课 - 死亡课程节选

You can say "Why don't you" when you want to suggest that somebody else do something.

当你想建议他人做某事时，你可以说“Why don't you~?”。

Why don't 课堂 - SpeakingMax英语口语达人