Keep the costs down...
The EC145 is certified as the BK117 C2. This allowed Eurocopter/Kawasaki to keep the certification costs to a minimum. You might be interested to note that as a result of this EC were able to use the large screen by applying the regulations in force at the time of the certification of the BK117, the screen does NOT conform to birdstrike criteria in force at the time of the certification of the C2; this has been a sticky point with the CAA.
As an aside, the choice of a plank wing IFR FMS for a helo destined for a lot of SAR and police work was not wise. Try it and see.......