Same reason why none of these are simmable.
CG often only makes an old event simmable if there is a new event that takes more time.
Example, the assault battles became simmable approx the same time that conquest was released.
For some of the events below to become simmable, we would either need another time sink, or CG decides to be generous with their R&D budget and spend money on the programmers to make said change for no monetary reward.
Advanced Fleet Mastery:
• Admiral’s Maneuver
• Discarded Doctrine
• Dark Sovereign
• Endurance
• Executrix
• General’s Command
• Home One
Special Events:
• Defense of Dathomir
• Endor Escalation
• Galactic Bounties I
• Galactic Bounties II
• Ghosts of Dathomir
Resource Events:
• Contraband Cargo
• Smuggler’s Run I
• Smuggler’s Run II
Mythic Events (only partially simmable):
• Artist of War Mythic (Grand Admiral Thrawn)
• Daring Droid Mythic (R2-D2)
• Emperor's Demise Mythic (Emperor Palpatine)
• Grand Master's Training Mythic (Grand Master Yoda)
• Pieces & Plans Mythic (BB-8)