Because COMMUNITY, like PARKS & REC, is too low-rated to be a centerpiece of their brand. NBC has, for two years now, been trying (in their phrasing) to be broader, not smarter. All they have to show for it are shows that continually come in under their niche-but-acclaimed veteran comedies. (PARENTHOOD fits this pattern on the drama side.) With THE VOICE, THE BLACKLIST and CHICAGO FIRE they've managed to stabilize the first half of the week and are on more solid ground ratings-wise than their absolute nadir, but Thursday nights are still far from Must-See TV, even though it hosts some of their best shows by quality.
Words don't deserve that kind of malarkey. They're innocent, neutral, precise, standing for this, describing that, meaning the other, so if you look after them you can build bridges across incomprehension and chaos. But when they get their corners knocked off, they're no good anymore…I don't think writers are sacred, but words are. They deserve respect. If you get the right ones in the right order, you can nudge the world a little.