All emotional reactions are "manipulated" - we choose to expose ourselves to situations wherein we might feel emotional reactions of various sorts. Why is art, "negative" reactions or not, any different?

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.

I lost my mom some years ago. It definitely just hit me, and I was kind of in an odd place in life at the time. I don't think I really processed it all well at the time.

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.

I didn't believe "ugly crying" is about negativity. Rather, the "ugly" bit is about the abandonment with which one cries. One is so invested in the emotions (whatever those may be--it's not even a continuum of good/bad but rather a huge, high dimension vector space) that one abandons propriety and self-respect and just cries. It's about investment due to the exceedingly high emotional resonance with the subject matter.

This is my understanding. Caveat: I am not a person who cries much, if at all.

there are many things in life which cause crying which are not negative.

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.

I understand your question, and it is hard to describe. Our brains are pattern generators, and it "feels good" to resonate with patterns we've already experienced. Neural circuits create patterns by strengthening connections upon our experience. This is particularly true as we get older and our brains become less plastic. Lesser used patterns become harder to access as they are no longer reinforced as frequently. However, this feels less good for our brains, and we value novelty.

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.

Because art can be seen as manipulation, or it can be seen as tapping on the deeply fundamental hooks that make us human. Feeling affects from an artistic representation tells us something about the human experience that goes beyond our intellect. Its closer to something spiritual rather than something analytic.

Because it is a form of learning.

Also ugly crying is not always a negative reaction. It's empathy which is important to our survival (and also wonderful).