Why is only the ? and ! put at the front and upside down of a sentence in Spanish?

https://yiffit.net/post/8361682

Why is only the ? and ! put at the front and upside down of a sentence in Spanish? - Yiffit.net

Why not periods? Why doesn’t every sentence in Spanish that isn’t a question or exclamation start with a period floating in the sky?

Here’s a period: .

Here’s an upside-down period: .

Hope that clears things up.