Why is the 6pm SImpsons being shown from Season 2 again

Since last Monday, Channel 4 have been showing the Simpsons from the second season (1990) againfor the third time since they took over from BBC2 last year. Why could they not show seasons 11 and 12 (1999 and 2000) on that slot. Especialy since Big Brother has been taking the Friday night slot

Episodes that are terrestrial premieres, such as those from 1999/2000 cost alot more than repeats of the early series. As the epidodes shown at 9pm on a friday are in prime time, and therefore have a larger potential audience, Ch4 will show them then, rather than at 6pm, when they wont return as much money.