We can't have it due to poor implementation and design by developers, fear that players are too dumb to understand or capable enough to utilize, and probably some story reason as a cop out.

-There will be no major job changes in 3.0. This has already been confirmed.
-They have low ambition of expanding on secondary stats.
-They view secondary progressions systems(FFXI: merit points, Rift: planar attunement) as just something that happens when the levels are too stagnate. We likely won't see this until after 3-4 level increases despite the fact we're rolling in xp that can't be used.
-Secondary abilities will never be game changing or provide meaningful choice options. -Main class abilities will fall under the same concept as there is no talent/skill mutually exclusive choices to define playstyles.
-They have little understanding of "clutch"/ "turn the tide" moments with reactive abilities/mechanics. They also don't know how to reward players properly for acting on reactive abilities.
-Development/implementation time is excruciatingly long. If we were to get it, it would take close to 6-7 months before we would see even the glimmer in their eye for it.
-THEY HAVE TERRIBLE CODE AND CANNOT FIX THIS AGGRO BS THAT HAS BEEN IN THE GAME SINCE RELEASE. HOW HARD IS IT FOR ENEMIES TO CANCEL THEIR IMMEDIATE ACTION, STOP CROSSING AN ENTIRE FIELD, AND GO TO A DAMNED TANK AND BEGIN THEIR ATTACKS AS SOON AS THE TARGET IS CHANGED? WHY IS THIS STILL AN ISSUE A YEAR LATER?