Damage is used as a proxy metric for player skill. As such, damage is the main thing that players on all roles care about (supports included). That's part of the reason why the 'trinity design' in this game has atrophied over time. Support functionality just isn't valued by the community the same way that raw damage is. That's also partially a function of a move away from pass-fail support checks.

You can argue that the value of tanks and healers is at least somewhat protected from this by a combination of fight design constraints, LB penalty, and role buffs. But the Physical Ranged/Magical Ranged split (or more accurately, Physical Ranged/Magical Ranged Support/Magical Ranged Damage split) is a lot more tenuous and much less enforced. I think the bottom line here is that all ranged jobs should provide an equivalent level of damage output and support functionality to each other. Large discrepancies in damage, like what currently exists between PCT/BLM and the other ranged jobs, are a problem.

Most people are happy to offload support functionality and the associated damage penalty that comes with it to another player. If you need that raise, just bring a second Caster with raise. If you don't, lock out the prog Casters. SE fully understands what the problem is, but I think they're afraid of rocking the boat. That's exactly why popular jobs stay popular.