Because they don't know how to govern, House Republicans fall back on threats and extortion. Whenever Democrats make an agreement with the House, the crazy minority insists that Dems surrender on yet another cultural issue. And that's why they simply can't run a stable government. Via the Washington Post:

Leaders in Congress slipped Sunday in their last-minute scramble to head off a looming government shutdown deadline that could shutter vital services at the Transportation Department, strain food stamp programs and put housing assistance for millions of families in jeopardy.

With some federal funding set to expire in less than a week, House Republican policy demands — on issues ranging from LGBTQ rights and abortion to national security concerns on immigration and competition from China — have slowed talks that had appeared to be close to yielding a breakthrough. Lawmakers abandoned tentative plans to announce legislative text on a deal Sunday evening.

Instead, legislators privately say another temporary spending extension could be necessary to avert a partial shutdown that could ripple into the winder economy. Roughly 20 percent of the federal government will close on March 2 without action. A deadline for the remaining 80 percent awaits just a week later.

Every time they reach a deal, the Crazy Caucus stamps their feet and demands yet another culture-war concession. It appears they don't really understand how actual political deals work.