the districts are a nightmare logistically and unneccessary expense.
Yeah, a nightmare for the poor local saps who have to organize everything. And an unnecessary expense for the poor blighters who actually attend.
But a hand-over-fist money-making enterprise for the org.
They will never ever ever drop DCs (though I would not be surprised to see them scale it back to 2 days). They are huge huge money-makers for them...I worked in accounting one year, and in a "money-collecting depot" (where the contents of the big cardboard contributions boxes were aggregated before being taken down to accounting) for several more years. The take for 3 days can easily exceed 6 figures (US dollars). Multiply that by dozens of assembly sites in the US, and see how it all adds up. Then add in Canada, Western Europe, etc.
DCs are the "black Friday" for the Borg.