Skyhigh,
I note your concern but beware of making assumptions. I used to fly a police helicopter in an area without air ambulance cover; we used to fulfil both roles. From my own experience, what is really needed is dedicated aircraft for each role. Would we expect a military fighter to fly as a bomber, or a transport aircraft, or vice versa? I would hope not; each cannot fulfil the other roles effectively.
A police helicopter is not like an empty "white van" inside, nor is an air ambulance. Each role requires specialised, fixed equipment. To convert from one role to another may need an engineer using special tools.
All of the role equipment is included in the all-up weight of the aircraft; the maximum weight of the aircraft cannot be exceeded. Performance limitations due to takeoff / landing altitude and temperature may mean the maximum weight cannot be flown, so removal of this equipment may be essential.
Physical space limitations of the cabin can make it very difficult to fit a stretcher. One type of police aircraft that I flew cannot accommodate a stretcher unless the observer's seat is completely removed and both it and the occupant are left behind. Not good if the next job is an urgent police job with the observer left high in the hills, waiting for the aircraft to return; but at least that would increase the hours flown - but unfortunately the extra would be wasted hours.
If role equipment such as the Nightsun searchlight and the camera needs to be removed to save weight, it takes a finite time. If an aircraft flies in one role, it may be unable to go to a different job role without a retrun to base for an engineer to remove one set of equipment and fit another.
By trying to make one aircraft fulfill both roles, it may become only partially effective in either or both; certainly the response times may be increased to an unacceptable level.