Because it sure should.
Somehow, it's gone almost unnoticed that Marine Corps artillery units are serving in Syria. Consider this item from the Military Times from just a couple of days ago:
U.S. Marines are conducting around-the-clock artillery support for American Kurdish partners battling ISIS in its de facto capital of Raqqa. That support has become vital as Kurdish forces have hit fierce resistance as they inch closer to the city center, according to on the ground fighters.
If American infantry was on the ground (other than the special forces, which you can bet are on the ground, and probably providing the artillery spotting for the Marine Red Legs), you can bet you'd have heard about.
But artillerymen? Apparently we just don't count.