Bill Bryson claims in one of his books that this formation comes from the Irish language. I believe certain people here say “to the hospital” and others don’t. However whether that’s the influence of Merkin TV or an older usage I haven’t a notion.
But that was my point. People don’t normally say “to the school” when they attend school (your first statement), but some people (cultures) will say “to the hospital” exclusively, and others will say “to hospital” exclusively, no matter what the intention.
Here in the south, I have often been asked if I have “a sinus” if I’m having a really bad allergy day.
I’ve heard “the AIDS” around here but I think it’s only used jokingly. Yeah we’re sick.