Because that's how things are
Because humans are all like that
Because, Because, Because; Because I don't have the balls to try and build something, only the infantile urge to break things
You can always tell an incompetent coward by their words; simply believing that you can do or be better than what you see proves that the world doesn't "have to" be the way it is.
Yakuzaboi doesn't need a name; "piece of shit" is fine as a placeholder 'til his own actions bring his death.
Be nice if MC would help him along with it, but manga requires lots of preamble, lots of postscript, and lots of clash, clang, sturm, and drang... with never any form of resolution.
I like that the MC went for beating the shit out of that little bratty fucker; more of that, for sure.