because hospitals are so clean/disinfected
I'm inclined to seriously question that, since it seems hospitals in general are not clean at all, to say the least:
Why Aren't Hospitals Cleaner?
Commentary: Not All Deadly Infections Come From Dirty Hands. Check The Lab Coats
www.cbsnews.com
The Latest Dirt on Hospital Cleanliness
An infectious diseases specialist reviews the evidence for contamination sources in healthcare facilities.
www.medscape.com