One legend or local legend may only be taken as a reference. But a legend of global nature across cultures definitely says something. Overlook this fact is not scientific.
I agree. Humans have a strong creative imagination for how things could be and how they could have been, a strong tendency to interpret the world in terms of agency and teleology, especially in explaining the unknown, and an equally strong tendency to generate narratives, to tell, embellish, and elaborate stories.
Mythical, magical, supernatural, legendary creatures, spirits, sprites, fairies, gods, devils, demons, etc., recurring across many cultures. There's no evidence any of them are or were real. On the other hand, we do have evidence of many extraordinary creatures that are real, and none appear to have supernatural powers or abilities...
... Why should I think the same way as you do?
I don't think that's possible, we all think in uniquely individual ways. But there are useful tools and aids to thinking that are worth considering, like rationality, scepticism, critical thinking, Bayesian thinking, etc. These can help clarify and resolve matters, e.g. help in distinguishing fact from fiction, probable from improbable, real from unreal, etc.