Lazy writing paired with conflicting visions behind the scenes are the culprits, most likely. Sometimes people get an idea and are too lazy to build it up properly and believably, and too lazy and uninspired to properly follow through with it. Similar to the case with Val Zod and Power Girl, Supergirl had some black guy in a wheel chair for a boyfriend for all of...like 2 issues. Then the writer got taken off the book--Mike Johnson, I think--suddenly and that black guy just kind of disappeared. I literally think he just disappeared, as if he never even happened. The incoming writer had no interest in pursuing that.
Considering one is Power Girl and the other is Supergirl, I chuckle at the parallels with these situations. Speaking of which, whatever happened to that other black guy Supergirl was with? The one who worked for Cat Grant? I'm pretty sure he just literally disappeared, too, probably without any explanation.