It's pretty simple, actually, once you understand the concept of the Ruling Party (which represents, and is owned outright by the Ruling Class). Ruling Party Republicans and Democrats alike in the Senate hate the wings of their parties (which actually at least try to represent the original ideals of those parties). Hence McConnell, McCain, Graham, and other such RPR (Ruling Party Republicans) hate and fear conservatives like Ted Cruz and his fellow conservativesalmost as much as Schumer, Feinstein, et al hate the Bernie Sanders wing in the Senate. But the existence of the filibuster still allows McConnell and McCain, Schumer and Feinstein, to get together and block anything they don't both agree on. Hence it will stay, because both sides agree they want to destroy the Trump administration, agenda, and presidency.