So you also use a semicolon if you are separating a list and the list includes phrases separated by commas. For example:

My favorite things are lions, tigers, and bears; sugar, spice, and everything nice; and the ol' red, white, and blue.

I came up with that in thirty seconds so admittedly it's a bit nonsensical, but there are valid reasons to structure a sentence this way and a semicolon is the only thing helping those independent phrases stay separate and thus help the sentence make sense.

That said, I love semicolons in general; I use them for fun and for variety. They are useful for slightly adjusting the pacing of written communication, since the reader won't treat them exactly the same as a full stop.

If it was actually useful... People would learn it organically and not need it to be explained.

People don't learn how to read "organically;" you need instruction. Learning how to use punctuation is a part of that instruction. You learned how to use a comma or a period way back in elementary school, you just don't remember specifically learning it. And a semicolon is a perfectly useful piece of punctuation.