Pressed discs (like movies) are physically… pressed. They make a metal mould which is then stamped into melted plastic to make the pits and lands and then coated with a metal film to make the reflected backing, filling in the pits. This makes manufacturing of millions of disks extremely cheap since it takes seconds per disc. Burning commercial disks individually in thousands of burners would be way too slow/expensive.
Some things make more sense with additional context. Like, Europe was on the PAL standard while Japan was on NTSC, so even if you put them both in the same region, they couldn’t watch each other’s discs, so the region code could be re-used without it actually conflicting.