Simply put, there's often nothing better to put in the slot.
The two primary sources of DA in gear currently are Brutal Earring and Pole Grip. Pole Grip v Sword Strap v Rose Strap is very situational, but Pole usually wins because either Sword breaks your x-hit/forces bad swaps/sidegrades due to the job in question or Rose is unnecessary for your x-hit. Brutal Earring is much less situational; the DA has to be severely devalued for it to be undesirable. This really only occurs when you get into using non-Jailer multihit weapons. On anything that can hit 3 or more times Brutal is a poor choice of earring, and if you have an acc+4 earring in that slot (Hollow for instance) that earring will be better than Brutal in any uncapped hitrate situation (provided you fully benefit from the accuracy) using a non-Jailer OAT weapon.
EDIT: Why you should
rarely use DA? I'm not sure. Things like Ares Flanchard/WAR AF2 legs vs Homam/Byakko's are pretty straightforward, but other than obvious cases like that and the less obvious Aesir vs Forager's (Aesir only wins in high pDIF/capped fSTR situations), I'm not sure why it would be rarely used aside from scarcity.