I learnt about passive voice by deliberately writing that way. When I started writing about science (and I won't say how long ago that was), passive voice was seen as a sign of objectivity in science.
I was taught to write, "the variables were selected", "the subjects were observed", "the output was weighed" et cetera.
Thank goodness, common sense (and the active voice) is winning. Despite grammatical convention, human choices always drive science, and bad science is still bad science, even when it is described in the passive voice. Conversely, active voice doesn't change good science into bad science.