The guys that have that either built it much faster prior to becoming AA (pre merger), likely built it up by not having to call out because they had <80 hour lines and actually had time to recover before their next trip, could simply drop or trade their trip, or are Blue Falcons who fly sick because they don't want to use their precious sick time and don't care if they get others sick.

The current 60 hours a year for a newb with ~90 hour lines and the complete inability to drop or even trade... they'll never build up a high sick bank, especially if they call out sick when sick.