It's a premise with many flaws, but chief among them is that watching robots fight just doesn't look very, you know, entertaining. Much like this movie, actually.
The reason it doesn't look entertaining (and by "it," I mean both the fictional sport and the movie) is basically summed up by Jackman himself in the trailer's voice-over: "The human body can only take so much. But the steel never stops."
That's meant, of course, to be an endorsement -- if people can fight, imagine how much better robots can fight, amiright? On the surface, yes, perhaps, but there are two fundamental fallacies at work here: 1. If the steel never stops, as you say, Hugh Jackman, than riddle me this: How can there be a winner or a loser? If the steel never stops, then a fight between two steel things essentially has no stakes. 2. And more importantly, adding the suggestion of infinite capacity to a contest between two things doesn't make it better, it makes it boring.
Hear me out: The whole reason we watch sports like boxing or mixed martial arts in the first place is to see the limitations of the contenders -- for the viewer, the punishment is the reward. All making robots fight does, then, is to remove the whole reason we were watching -- the contest no longer means anything. You might as well make robots run marathons. Fuck it, have robots star in this movie. Who gives a shit?
Plus, there's no blood. And you know how we love blood.
Read a real review of Real Steel!