I support this because most don't even get 5 useful crossclasses.

SMN: raging strikes, quickcast, bliz2, surecast, then 5th has to be quelling strikes, which is barely ever an issue for smn, and hawk's eye which was completely irrelevant till 2.1 and even now barely useful at al

PLD: foresight, bloodbath, stoneskin, cure, then what? Skull sunder: redundant, fracture? barely better potency than fast/savage/rage combo. Mercy stroke has very limited usefulness as it is. Even setting ss and cure are borderline redundant for pld. So then you're only left with 3.

SCH: with a WHM in party as well 2 of their 3 useful healing-related cross skills aren't used. SCH has more offensive crossclass options than healing ones.

The heavy-handed Virus nerf leaves one of BLM's 5 useful crossclasses useless if a SCH is present, and calling 5 skills useful is a stretch.

Ideally each job should have at least 6 so there's some room for choice depending on the situation. We're far from that.