I can't explain the obsession, but I can explain why they remain so prevalent: put simply, zombie AI is much easier to program than intelligent AI. So instead of making a military shooter, developers can make a zombie shooter for less programming costs, add more enemies, and sell more copies thanks to the word "zombie" in the name.
Sadly, the developers of Gran Turismo realized this too. In Gran Turismo 5 Prologue, you race against pathetic zombie drivers, BUT THERE ARE MORE OF THEM.
Sadly, the developers of Gran Turismo realized this too. In Gran Turismo 5 Prologue, you race against pathetic zombie drivers, BUT THERE ARE MORE OF THEM.