From Vox:

“When [members] look behind the curtain and the emperor has no clothes, then it becomes contagious,” said James Wallner, a political scientist and former executive director of the Senate Steering Committee. “And that’s what leaders don’t like. So far they have been successful in convincing members that it’s not good for the majority.”

[…]

“What the leadership would like to happen is for members not to act, same in the Senate, because then you can’t control what happens next,” Wallner said.

[…]

“Members who theoretically want to advance an agenda aren’t doing so, because they think the majority is very important,” Wallner said, but at a certain point, that all comes to head.

“You can’t bottle up stuff forever,” Wallner said. “It keeps getting worse. At some point, things have to change. There is always another election — and then when that happens, we are not going to get it, we are never going to get it, because the parties aren’t unified.”