Each episode uses 2-4 chapters worth of material. Though the reason they do not catch up, but so easily could is because they want the hype to be real. They also do not want to ruin anything, like if they accidentally leave something out or throw something in. It's hard to explain but they need to stay at least 50 chapters behind in the manga, so that everything works. Since the manga ends this year or early next year, the anime no longer needs filler. It has already been confirmed that there is no more filler this year!

but why didn't they say no more filler at all? Well i think by not saying that, they also confirmed that the manga will go into 2015! But it could also mean the opposite... if the manga ends this year, then so will the anime, i just did some calculations... If there is an episode every week for the rest of the year, and has 2 chapters each (sometimes 3) then it will be completely caught up by the last week of 2014. But who knows, we'll just have to wait and see.