The White House really doesn't want any. And a lot of Republicans really can't live without them. And viewed through a lens of political strategy, they're both right. Whereas the Republicans know they need to change the emotional dynamic in the nation, so they want the process to focus on the gory and salacious details. There is, too, the fact that everyone, on every side, at every level, is a lawyer.
Lawyers loathe legal uncertainty.
And there is no terra more incognita than an impeachment trial. You can hear the fear in White House spokesman Joe Lockhart's voice as he frames the stakes for his boss. I would suggest that that would be a situation, an environment, that is manifestly unfair to the president. Indeed, what's described to the nation as a musty debate over Senate rules and procedure may be seen as an effort to forge a coalition at a time when neither Democratic nor Republican leaders can enforce party discipline. And nobody's in control right now, not the Democrats, not the Republicans.