Why do we want to synthetically manipulate our brains into an emotional reaction, especially in the case of a negative emotion?
As another commenter points out, it's a good way of learning - about yourself, how you feel, about other perspectives. It's also, hopefully, a chance to grow - reflect on your past, your mistakes, how you've treated others.
Years later, when I watch a good movie that results in someone losing a parent figure, I'll often have quite a deep emotional reaction to it. But in the end I like these experiences. They help me look into those situations again and help me analyze the connection to losing my mom. Being in that state of emotion again helps me process it now that I'm in a very different stage in life.
This is my understanding. Caveat: I am not a person who cries much, if at all.
crying is absolutely not limited to “a negative emotion.”
if you’re struggling to imagine a crying situation that isn’t negative, i would heavily encourage you to indulge in more art.
So in the same way that riding a bike after a long time is much harder than it is to ride one when you use it every day, you can generalize this to something like emotions. It is bad to only experience one type of feeling all the time, and variety is good. Having a controlled, relatable medium lead you to experience a less commonly-felt emotion feels good. I don't know if I can explain why--maybe we have mechanisms in our brain for encouraging this novelty--but this is likely why we seek out these emotional experiences.
Also ugly crying is not always a negative reaction. It's empathy which is important to our survival (and also wonderful).