Let me answer this.
I believe it is because the Republican party deciders decided that they'd be better off in the long run if they could have more people in Congress. In an effort to make that possible, they used their energies to redraw Congressional districts to make as sure as possible by gerrymandering the ever-loving-f*ck out of as many districts as they could control. To be fair, this is something to be desired by weak thinkers, or thinkers of weak ideas in both parties. But the Republicans have torn that shit UP!
Because ... as a result of... it's difficult to discern cause and effect here... regardless, now we have the case that many districts are NOT COMPETITIVE. If there's no competition for the election, there's no meaningful exchange of ideas. That "compromise" that Adak pines for so loudly is irrelevant, and therefore not present.
For people with closed minds, made up minds, weak minds, this is very comfortable. And those comfortable voters are like great big steamy piles of poo for the ... they're not poo. But they're intellectually dead, because they're not taking in new ideas. And they're attractive to the carrion feeders politicians who'll eat any free lunch. Campaign money (PAC, SuperPAC, corporate) also factors heavily in this equation.
Competitive districts favor more moderate candidates, ones who are more likely to listen to the ideas of the loyal opposition, indeed, ones who are more likely to have reasonable ideas to be heard by their equally moderate opponents. Think about all the talk you've heard about the fear of being "primaried" from those in Congress. They aren't fearful of losing a fight to an opponent of the other party (unless the "other party" is the Tea Party), they're worried that they're not "conservative" enough. I use "conservative" in "quotes" because these labels are becoming less useful.
These districts are RIDICULOUS.