It hasn't always been what it is now. It does change. When we booked our first
DCL cruise in 2005, each cabin also received $200 OBC for 7+ nights and $100 OBC for 3-6 night cruises. Once they created the tiers of the
Castaway Club, on the 7+ night sailings you'd get $200 for silver, $250 for gold, and $350 for platinum.
These could be stacked in addition to any OBC you'd get from a TA, which ours gives us $200/cabin for a 7-night. So for our AK and Med cruises, we booked 2 cabins since our kids were getting older, so we got $700 OBC from DCL and $400 from our TA for a grand total of $1100 OBC.


Ah, the good ol days... when we'd sail 3-4x/year because the deals/perks were so good.
Then they dropped it back to $200 for all tiers. Then just dropped it completely.