One group might include lawyers who haven't figured out how to deal with CM/ECF, as apparently was true in this case, where an appeal deadline was missed because the lawyer did not know about entry of an order and was not registered for CM/ECF in that court.
The first case I had with CM/ECF was in Ohio, and I thought it was cool. Now, I get so many e-mails from the W.D. Va. system. Fortunately, you can set up your profile so that your e-mails from the court also go to your assistant, or whomever else you like.
I also get the e-mails from an MDL case via a Lexis service, which is not quite as handy.