You mean why didn't he take a WR shot between 2000-2004? Unclear. But in 2003-2004, he doubled in the 5,000 so running that as his off event in the lead-up probably took on extra priority for him and after doubling in the Championships putting energy into a WR attempt might be a bit much. He was Olympics-focused due to his 1996 catastrophe. I imagine in 2000 and then 2004 he didn't necessarily want to put the focus on anything else like a 3,000m WR.
Now 2001 and 2002 would be the prime years to go after. But in 2001 after winning Worlds, he took two record attempts at 1500 (missed by .12) and 2000 (missed by 2+ seconds). With a long season with a World Indoors Title at 3000 already in the book, maybe didn't want to bite off more than he could chew and opted to close it out with some lucrative 1500m wins on the circuit.
In 2002, he exclusively raced the 1500/mile despite it being an off year. He ran some fast times, but it seems like a missed opportunity to go for the 3000 World Record. That's the real miss IMO.