Index advisor in Navigator - why is it asking for DESC sequence?

I am starting to look at the big hitter items on my Index advisor...
it shows the keys advised, but when I say "show SQL", they _always_ show to create the index DESC on the fields.

I haven't been doing that.... and it appears to no longer advise a index be created. but is there a performance or database structure
reason I should be creating the indexes as DESCending?


example:

/* Creating index XXDATA.DTH_INDEX_00001
When creating this index the database connection should have a sort sequence of *HEX.

-- System name: Kxxx.xxxxxxxx.com
-- Database: Sxxxxxxd Advised Indexes for Sxxxxxxd
-- Times Advised for Query Use: 2586259
-- First Advised: 4/1/13 8:14:05 AM
-- Last Query Use: 1/14/15 8:26:52 AM
-- Reason Advised: Row selection
-- Estimated Index Creation Time (seconds): 00:00:20
-- Rows in Table when Advised: 569296
-- Average of Query Estimates (seconds): 0.0001
-- Most Expensive Query Estimate (seconds): 1
-- Index Type Advised: Not unique */
CREATE INDEX XXDATA.DTH_INDEX_00001 ON XXDATA.DTH (DTNO DESC, LPROD DESC);

/* Setting label text for XXDATA.DTH_INDEX_00001 */
LABEL ON INDEX XXDATA.DTH_INDEX_00001 IS 'Index generated from Index Advisor';