It simply comes down to that in spite of the fact that people still use older macs, including the g4, there is absolutely no incentive to continue manufacturing the old line - if someone wants an old mac, they can simply buy it for cheap off of someone selling their old system and upgrading to the newer and better products. I would think that the population of people who are in the market for a brand-spanking-new g4 is painfully small. Apple wants to remain competitive in this business - they're doing what any other competent company would do - phasing out stuff that won't turn a profit any more.