If that ever happened to me, you can be sure you would be written up. I working critical care, so if i need you to come in, I need you to come in. By not coming in, you're being unprofessional, disrespectful leaving the unit in a unsafe situation. I can't determine the census. The hospital can't determine the census. We only staff RN's based upon our average daily census. If you're called off, you have the option to use PTO, education hours (every staff have so many per year), choose another day that week to make it up or not get paid. In my hospital it's not just RN's that partake in this. RT, NA's, US's even managers do this to help the org stay on budget. You can try to make whatever examples you want about chandeliers but bottom line is hospital are a business that need to make money- whether you agree or not.
In past, staff have called out for 4 hours only. It's not recommended or common because you probably won't be needed for the rest of your shift since we just found coverage to cover your absence. It's the risk you take.