That's a very incomplete analysis of the situation. Who controlled the TVs?
In 1990, 35% of TV households in the US had only one TV [
link]. If
Star Trek conflicted with something that the parents wanted to watch,
Star Trek wasn't getting watched, regardless of how free and over the air it was.
In households with two TVs, it doesn't follow that any of the kids got to decide what was on the other TV. Maybe the second TV was in the parents' bedroom. And even when it was up to the kids, maybe
Star Trek was ruled out because one of the other siblings wanted to watch something else.
TL;DR - A kid who wanted to watch
Star Trek, even in the Berman era, often literally needed their parents' permission.