Do you, by chance, live in NYC? That is the only place I have lived where the meatbags regularly do not get out of the way of sirens. In most other places, they make a great effort.
This is true for everywhere I have lived in North America. Outside of NYC it isn't so much people not caring, as people not realizing that the siren is mostly to tell you to clear the way. A lot of people just take it to mean "stop where you are", when the actual intention is "move out of the way, then stop". I travel along a route near a hospital frequently, and it is incredibly common for people to be stopped in front of an ambulance, blocking the path, while the ambulance blasts their horn trying to get them to move out of the way.
If a meatbag comes upon a downed power pole, broken fire hydrant, fender bender, or sunken stretch of pavement they're usually pretty good about turning around or avoiding the obstacle. I haven't seen the same from these taxis yet.
More than meatbags?