Anime dvds/boxsets out of print?

Hi, can anyone tell me why anime dvds/boxsets go out of print here in
the United States? One example is Marmalade Boy. I find out now that
it is no longer for sale (I recently bought all 4 sets online but the
barcode was scratched out because it was =93out of print=94)

I=92m sure there are other anime dvds no longer being printed in the US.
Is it because their license has expired or is it because it didn=92t do
well? Will this happen to all the other anime dvds that are licensed
after a certain period of time?