While experiments allow researchers to propose answers to causal questions, in some cases, experiments are not appropriate. The most common reasons are

Answer: It would unethical to conduct some types of experiments on people

Explanation: Experiment as such serves to test a hypothesis, and based on the results obtained by the experiment confirm it, i. e become a theory. So experiments are needed to prove some of the assumptions, and the results obtained are knowledge that becomes part of the theory, so research is, in fact, a means of acquiring knowledge that is important for the theory.

Of course, knowledge is best if it is obtained by observing some of the phenomena being studied and researched, because empirical experience is the best confirmation of some scientific premise.

And while experiments are appropriate to the limits of humanity, it is inappropriate and unethical to go and subject people to experiments beyond that limit for research. Imagine testing a virus that is not sufficiently researched, and an experiment is conducted on people how they will tolerate it. First of all, this is not humane, it is not ethical, and it is not safe for these people, since it is still an unknown and untested virus.