I immediately remembered who Ensign Gates was when I read her name, even though her pic isn't posted in this thread. But, even after seeing the Diana Giddings article in Memory Alpha, I can only semi-remember her. The end of the article said:
I think you kind of made my point.
Ensign Gates had a prominent position as a BRIDGE OFFICER who was easily seen. The post has traditionally been run by a senior officer so it very much does draw your attention to that posting on the bridge.
I don't DISAGREE that others who have been seen throughout the series don't deserve a call out, but I think in the case of Ensign Gates, it comes more across as "Why hasn't she had one" just because of her posting.
Even Robin Lefler and Sonya Gomez, who had 1-2 episodes each had major call outs through other media.