I have never heard of you not having to write a hypothesis.

It seems to me that a hypothesis is an essential part of the lab. report, I could be wrong though…

I think that you generally need a hypothesis, because it’s supposed to be the point of the lab. You pose it as if it were a question: Is the world round? –> The world is round. Then you go around the world a few times, fall off a couple cliffs, and see whether the hypothesis can be backed up or not. The point of the lab is to prove or disprove the hypothesis, and to give you an interesting experience to remember the hypothesis by.

By lab report you mean in school or like scientific paper?

In school you of course do not need any hypothesis, because you’re usually doing the stuff to learn something, how is it working etc.

In my experience, we were taught and heavily encouraged to write the hypotheses regardless of this. Simply to get us in the practice of always writing them.