Res utility isn't a caster thing though.

Res was a SMN thing because it was an Arcanist thing, because of SCH.
RDM has a res, because it's a Red Mage.
BLM came before both of them.

If we get a fourth caster, it shouldn't, and there's no reason why it should, have a res.

But I'm fine with it being this way.

Physical Ranged DPS have a gradient of utility, from MCH having least, to DNC having most.
A similar paradigm for casters works well too, BLM least, RDM most.