Well, MLB did try it. And successfully, with McGwire vs. Sosa. But then how did that really turn out? The fallout there was - they both were using steroids, or were at least strongly suspected of such. And that lead to a whole great big scandal that probably still isn't over yet.
Now MLB is getting headlines again for another cheating scandal.
MLB has decided to live and die on its history and tradition. The problem they keep facing is every time history gets challenged, it turns out someone did so illegally this time. (And it also hurts that everyone is willing to ignore all cheating pre-1990.)
I would not be surprised if they decided to hold off on pushing Trout as the next big thing for this reason. What would the fallout be if Trout - already maligned once with HGH rumors this off season - really wasn't clean? The NBA never had this problem with Jordan. His biggest smirch was some gambling issues that were easily sidestepped because it turned out, no one cared...