Why do they do that?

food theory:

I pressed the wrong button

So then why does the button even exist?

just use it anyway

exactly, do your own thing

Me who never reads the instruction, putting the popcorn and presses the button.

I still use it and nothing's exploded so were good

There is actually a good explanation for this: popcorn packs are best when cooked at a certain temperature, and different microwave models have different temperatures.

Very good point

I still use the button

:0)