First of all, React has nothing to do with http. Underscore is not a templating engine.
But ultimately if you don’t like it, don’t use it. Period. Do what you want.
Why do I use it? Because I find it an incredibly powerful tool for organizing and structuring the different parts of my app. I can’t imagine working on an app the size of what we have at work without something like it. It would just be a nightmare.
Yeah, you can get some of the same functionality with those templating engine. But I like the way React works better, how the pieces communicate.
Use it or don’t. When people ask me “Should I learn x, y, or z?”, I respond by asking which is more likely to land a job. Scan the want ads where you are and see how many times you see Mustache mentioned and how many times you see React.
Part of learning is the humility to say, “I don’t know this. Someone else is more experienced than I am. I’m going to trust that they know what they are talking about. It may not be what I would choose, but then, they know more than I do.” Having spent decades as a music teacher, I’ve seen a lot of the “I don’t want to learn that because I don’t see the value in it” attitude. They usually don’t fare well.
Do or don’t, it’s up to you. Frankly, when I first started React, it didn’t make much sense to me either. It wasn’t until apps got larger and I got better at React that it started to make sense.
As far as listing the benefits of React, there are plenty of resources on the internet. If they didn’t convince you, then there’s no point in me trying.