It seems like it would be strange to reject as an answer to "why do blind people tend spend less on lighting?" with "Because they don't tend to use the lighting, because the lighting isn't useful to them, so they don't turn the lights on as much (unless someone else who isn't blind is there).".
How else would you answer that question? (modulo little wording changes and such)
But no, in a meaningful sense it's not a true statement about the world. It's a good guess, and for a statement that simple, there might be no need to go further. For a statement about why a volume is full with too many files, the point is that a nice-sounding "if only" isn't something you can test or be certain of.
Your answer about blind people is a very good guess as well, and the same one I would make, but it's not data.
A counterfactual requires posing a situation with changed facts. I stand by my statement, saying "X because not Y" is not a counterfactual on its own. "not Y" is still a (potentially) factual statement. And guesses still aren't counterfactuals. "Maybe the lights aren't on because we didn't flip the switch?" That's a hypothesis, and a testable one. Still not a counterfactual. If we know the flip hasn't been switched, then it's just a fact even if the statement is in the form of not X.
Now consider the opposite. The lights are off because the bulb burnt out. That's a lot less ambiguous. If you want to doubt the causality you've got to get all mystical.