Our 10 year old gas fireplace looks so much nicer without the wire mesh screen, just the glass front. The glass seals to the face with 4 spring loaded clamps on the corners, and rope 'caulk'. Is the mesh screen panel in front of the glass necessary? or is it just to give it the look of a spark screen ?
Without seeing a picture, I'm going to assume you're talking about the "safety screen" that now comes with most fireplaces.
It's necessary for manufactures to provide them, but whether you put it on or not is up to you. The intent of it is to stop small children from burning their skin on it if they get too close to the unit, but if there are no children in the house then it serves no point.
The mesh screens or curtains on a fireplace are meant to stop embers that pop off of logs from escaping the fireplace and burning carpet or furniture. When you have the fireplace burning, the glass doors would be open so something is needed to keep sparks and embers in their place.
You say you have a gas fireplace, but much of the trim is "one size fits all", so it might not make much sense to have a screen with an exclusively gas fireplace, but it's going to come with the trim kit anyway.