The bright idea of concentrating artillery capability (tubed artillery capability) in the 155 mm howitzer/medium artillery was never appealing. There are so many situations where this kind of 105 mm gun, towed, self propelled on wheels, self propelled on tracks, easy to transport by chopper, easy to load onto any kind of aerial logistics support aircraft (meaning, aircraft smaller than the C 130 can be used) is ideal, the amount of ammunition that can be transferred in a particular load compared to the corresponding number of rounds for the 155 mm guns being one.
As an incentive, it is worth looking up the amount of surplus 105 mm shells lying with a friendly country that collaborates with us on military production, shells that they cannot re-sell, and might well be willing to transfer for a relatively low price.