I would think one factor keeps showing up be it urban or rural...aircraft operating right at the very limit of performance due to combinations of operating weight, altitude, temperature, and landing site conditions...confined area landings and takeoffs for instance. Anyone that has flown Jetrangers....with the loads that EMS ops requires understands what that is all about
The latest accident posted above was in Colorado, summertime...thus hot...elevation was somewhere between 7,000 and 11,000 msl thus a significant Density Altitude. It will be interesting to see what the investigation reveals.
I think other issues like "Wires" and wire strikes are another common hazard to both urban and rural operations.
Night flight in marginal weather plainly is a great threat to rural operations....fewer ground lights...weather reporting sources further away....much easier to find yourself inside a cloud without planning on it.