plasma cinema display not compatible with power mac G4.Why?

Often the reason is the driver for the machine is not available. I have a Samsung that I intended to use with my MacPro and when it didn't work I call Samsung and they said they only made drivers for windows machines. Kind of frustrating but such is life. Other reasons can include the scan rate of the card is too slow to sync to the monitor or not enough video RAM to push it. Sorry to say they are always trying to make us buy new machines if we want to play with the newest attachments.