Neither are horses, eagles, lions, or the other constituents of such mythological creatures globally resident (or at least were not until we humans brought them around the world).
Reptiles, on the other hand, exist nearly everywhere.
And the "dragons" of each culture are
significantly different. They aren't a "worldwide myth" - many cultures simply have myths about large reptiles. The description of those creatures varies so wildly that you may as well also call a centaur and a minotaur the same thing as calling all of the reptiles dragons. They are named as such only due to the immediate reactions of other cultures noting the similarities - that they are all
giant reptiles. THere really aren't any further similarities at all.
Ancient people exaggerated and compounded upon the real-life animals they saw around them, or heard about from traveler's tales. Stories were told, and exaggerated, and retold, until we have such fantastical creatures as gryphons and dragons. That's all.
When you know you're going to wake up in three days, dying is not a sacrifice. It's a
painful inconvenience.