If I were to guess, it would be the old production thought process. Trek is a bonfire franchise, and we just have to keep the fire burning. It doesn't matter what we throw on the fire, as long as it keeps burning. Each episode was a piece of firewood so that it wouldn't die. They thought they had utter fan loyalty, and that the way to cultivate that was to not push too hard in certain areas.
When writers like Bryan Fuller or Ronald D Moore tried to liven up the characters, or make them more real, they were told to stop. They wanted something that one could watch at any point, in any order, and not have to worry about things like character development, serialization, continuity, or anything like that. To them, TV was still like the days of the 1960s and 1970s, where reruns didn't happen, continuity didn't matter, and you could retell the same story ten times, because there was no way for them to rewatch and see what was going on.
That's the thought process. We're doing sci-fi Bonanza. We have to have something down for the week, it doesn't matter if it's good, we just have to get it done. I think that's why they hated DS9 so much. It couldn't be picked up by Joe Bob and Cletus on an afternoon and know automatically what's going on. Voyager probably could, or was so non-offensive, that it could.
That's what they were going for. Something that would keep the fire going, no matter the quality of the firewood.