I think a lot of times people just don't care. Especially in places like hospitals, they deal with a million people every day and I'm sure that patients can easily become just another body they need to treat. Don't get me wrong, I'm not defending them, but I can see why they're less than careful about people's names.
I don't know how many times people have gotten my name wrong. Even when I'm spelling it out for them, they can't seem to wrap their minds around the letters I'm saying.
I was trying to get into a building once and the security guy had to look up my name on the visitors list. I spelled my last name for him, gave him my ID with my name on it, and I watched over the counter as he typed my last name wrong. I spoke up and corrected him, and he re-typed it... wrong again. It took him 3 tries to get it right... my last name has 3 letters in it, not that difficult, folks.