Nothing special that I know of, but there are a few factors:

1. Some flyers just like the bulkhead seats.
2. Popular with pre-boading (disability blue sleeve) passengers due to the easy-on, easy-off.
3. There is a psychological factor of "first class" (close to the restroom, entry door and away from the engine noise) seating for those who are used to flying other airlines.

Just my $0.02

I'm an exit row (extra leg room and no kids) guy for my 90-100 flights a year.