The only players who want their job to have a privileged status over the others are ones who don't feel that they can confidently compete when things are fair.
If in the sense of being allowed job X over job Y, sure. But that also wouldn't be an unfounded fear, given how quickly PF can narrow down what's permitted. Why take a BLM to a fight if a MCH cycling its 123 and hitting its CDs on CD will put out as much as a wholly optimized BLM and most players won't be able to fully optimize said BLM anyways, thus underperforming the easier option?
So what if a fight makes you get off the couch and actually move as a caster?
The "what" in between is the rDPS gap from movement that distinguishes one fight from another and one job from another. And that distinction is something we'd generally want, no?
Movement doesn't equally tax all jobs, nor does each fight have equal movement requirements. If a given caster is balanced for a given fight, they will underperform for whose movement requirements that tax their capacity more and overperform for those that tax them less.
Taking something like a BLM is therefore a doubled risk: First, will the fight's mobility requirements exceed what the job is balanced around? Second, how likely is the given BLM player to meet the kit's potential in that fight?
Which brings us back to the core problem:
If all jobs have precisely equal rDPS despite having varying levels of difficulty¹, any harder job provides greater risk for no reward.
If all jobs have almost precisely equal rDPS despite having varying levels of difficulty¹, any harder job provides greater risk for too little reward to exceed the likely loss to learning or external difficulties (mechanics, raid-leading, tilt, etc). In that position, even as difficulty decreases and would otherwise loosen strictures on what jobs are permitted, so too is the risk of taking of those jobs because of how much greater those jobs underperformance will likely be as those players take the steps to learn them.
¹ Let "difficulty" here refer to the effort required to master a job up to a point of diminishing returns that would be wasteful for a player running a particular form of content to exceed. (For instance, a MNK doing only Extremes at most wouldn't exactly need to have perfected Optimal Drift... while a MCH would have already capped out all there is to learn by that point, between selecting between a standard or delayed opener.)
Or, put more simply, unless the simplest jobs are un-gutted to be more on par in terms of depth, perfect rDPS parity between jobs would effectively just push any players attempting to learn harder jobs away from mainstream play, relegating them to off-meta 'ego picks'.