Why did they never facelift the E46 M3?

[Mike_C]

A very simple question, but why did they never facelift the E46 M3 with the rest of the range? Yes it got the LED tail lights and interior changes (HVAC update, etc.), but the front end never got the facelift update the rest of the range received and I wonder why not? I heard one theory that said they felt the original was more aggressive, but I fail to believe that is the only reason. It always sold in decent volumes, so I'd have though the tooling investment in the bonnet and wings would be covered...anyone heard the real reason?