I understand that part of their reticence has to do with who they have been trying to call before the committee. People with no connection to Trump or were not associated with the Trump administration in January. The word is that if not now then after the election, the new committee will start calling people on the democrat side who actually had skin in the game like Nancy Pelosi. According to the Constitution, the House (and that means the Speaker) has the responsibility to protect the capital. What did she know and when did she know it? We know that it was highly recommended to beef up security with National Guardsmen or local police. She turned it down.
So, with the future looking bleak, maybe some democrats are wanting to be nice now before they put their own neck on the stump.