Whomever invented popcorn texturing should be brought before The Hague.
I don’t get it, why does it exist?
It is a quick and easy way to hide bad drywall work. The texture makes imperfections blend in.
Not just bad drywall. No matter how good of a sheet rocker you are gaps and tape will always be visible through paint without some kind of texture
Wait what? Is this specific to ceilings? Because I’ve hardly ever noticed drywall seams under paint
It can happen to any drywall really, and you have to look very close but you’ll see that joins are proud of the surface because of the tape and mud applied over them. It’s not the kind of thing that matters but if you have a very keen eye they’ll stick out like a sore thumb

This is what feathering your edges is for…

It just takes more time.

No, tape and mud will always show through paint simply due to the height difference vs the Sheetrock, unless you sand down the adjoining edges of each piece of drywall to perfectly accept the tape and mud which I have never seen or heard of then it will be proud of the surface.