One of the many interesting charts on SwayWhat's Polarization page is the below chart showing how Republicans and Democrats in recent congresses have been moving further and further apart.  Given this trend, it seems fairly clear why compromise seems harder and harder to come by these days.

In the last three decades, the political polarization of Congress members has skyrocketed, and with it, congressional productivity has precipitously declined. From only +328 Conservative, Republicans had become +620 by 111th. Democrats became more liberal as well, -189 to -354 Conservative. This party polarization greatly discourages working towards bipartisan, generally more moderate, solutions. [*1000 is considered completely Moderate*]

One reason I like charts is that they allow people to discover things for themselves, visually, which is always more convincing than having someone tell you about something second hand.  For more charts like this, checkout SwayWhat's polarization page.

– Ravi Iyer