i think the 17" was left behind for sale for the similar (but not the biggest*) reason apple sold G4 PMs after G5s came out. (*the biggest reason, of course, was OS9 bootability, i know.)
just a bit mismatched, old style stuff for cheap. apple is famous for maintaining the low end prices rather high. why rant about it now? i feel like this is something to be expected.
if apple didn't mind "commoditizing" their products with cheap low end products, then we would still have 5 GB iPods for sale at $150 and 500 MHz headless PowerMac at $500, etc.