Safety. Easiest. Best equipment. Stipend. Overtime training. Prestigious   

the last 16 years of my career after 34 years of flying helicopters IFR both on and offshore, single and dual pilot.  

On my very last check ride doing inadvertent IMC procedures the check pilot asked why I was not on an IFR operation.  Told him I needed that workload in a retirement job like another hole in the head, especially since the company would pay zero extra!!!  Took 16 years for the company to figure that one.  Three cheers for HR and very very incompetent management.

Ya get what ya pay for, including pilots willing to fly IMC.  Hint to those companies paying zippo!

BTW, I don't reccomend SPIFR in the HAA world - too much medical distraction and general BS.