The sketch artists is because some Judges do not allow photography in their courtroom. Sometimes for high profile cases, they don’t allow a lot of the media (news channels, etc.) so someone has to do some sketchesto show the public what the defendants and others looked like.
Court reporters are just to type out everything that was said, for review by the jury and attorneys later. Even if it’s recorded on video, it still needs to be typed out for the record.