Audi A6 (C5) 2.0 TDI - what's the point of getting this engine serviced every 30k miles?

I'm a bit concerned about my C5 A6 with the 2.0 TDI engine, and I'd love to hear from others with similar experiences - how often should this engine be serviced? Audi recommends every 30k miles, but I've heard it's not always necessary, or that some owners go longer without servicing...