Why "should" someone try to understand rather than judge?
What's the actual rationale for it?
What is the mutually agreed desired result of acting in those ways?
I don't really have an objective answer for you. I do find personal value in empathy, I get less mad when I can understand why someone did something I disagree with. It doesn't change what they did nor does it excuse it.
>What is the mutually agreed desired result of acting in those ways
Harmony.
Tossing the utilitarian perspective, being transactional and self-serving in your daily life tends to get you invited to less parties.
This is a philosophical question that man has sought to answer since the Stone Age. Much smarter people than us have dedicated their lives to the study of ethics and come up with wildly differing ideas, I don’t think you’re going to find an objective answer here.