When my dad was in the hospital, I had to deal with a lot of family members who couldn't be there in person. They all wanted me to keep them posted about any new developments. I didn't have to call every single one of them with updates, though. I kept a few of my dad's siblings posted about his condition and they passed on the information to others.
I think people just want to feel like they are in the loop when they ask you to keep them posted. I know I'm the same way if I can't get any direct information. Someone needs to keep me posted so I can plan what to do next.