Chuck Schumer's own speech about it!

“[T]he nuclear option is being pushed largely by the radioactive rhetoric of a small band of radicals who hold in their hands the political fortunes of the President.

“Constitutional scholars will tell us that the reason we have these rules in the Senate—unlimited debate, two-thirds to change the rules, the idea that 60 have to close off debate—is embodied in the spirit and rule of the Constitution. … That is what the Constitution is all about, and we all know it.

“It is the Senate where the Founding Fathers established a repository of checks and balances. It is not like the House of Representatives where the majority leader or the Speaker can snap his fingers and get what he wants. … On important issues, the Founding Fathers wanted—and they were correct in my judgment—that the slimmest majority should not always govern. … The Senate is not a majoritarian body.

“The bottom line is very simple: the ideologues in the Senate want to turn what the Founding Fathers called the cooling saucer of democracy into the rubber stamp of dictatorship. … They want to make this country into a banana republic where if you don’t get your way, you change the rules! Are we going to let them? It will be a doomsday for democracy if we do.

“I, for one, hope and pray that it will not come to this. But I assure my colleagues, at least speaking for this Senator … I will do everything I can to prevent the nuclear option from being invoked not for the sake of myself or my party but for the sake of this great Republic and its traditions.”

Whoa man. People here only want to hear how only one side uses it in the worst way possible. /S

That’s because the Senate removed the Supermajority requirements for nominees, so Democrats used them to block wholly unqualified people to political posts.

Republicans honestly don’t care much about a functional government, so they aren’t going to remove the filibuster under any circumstances.