Hi!
Convenience in the field. I don't normally want to carry my storage
device in the field (another pound in the bag) and it's more convenient
to have plenty of storage cards so that I can just keep shooting for
quite a while. Storage cards are not "serious money" anymore (at least
in the US) ... it's about $55 for a 1G SD or CF card at present.
For price of less than two cards I got 6 times more storage.
In Israel the prices are steeper and well, I wish I lived in States ;-).
At least for purpose of photography ;-).
Seriously however, I see your point. But having many smaller cards is
not like having single big one. I don't think that 8 MB cards cost mere
$450 (55 * 8 = 440)... I just checked Adorama. 8 MB card costs order of
$700.
When I go out for a session, I carry 6x 1G storage cards. I rarely use
more than two/three of them, but there are those occasions when things
are fast and furious and I fill almost all of them.
Point taken.
Boris