There is NO point in requiring attachment pieces to be worn. That is the same kind of "doing it because that's how it seems like it should be done" that creates 4/10 games. It encourages commonly manufactured pieces to be worn out to performance-driven events and that makes no sense.
This is an unbelievably simple argument, one which has no counter except stubborn mulishness.
You should not have to equip gear to turn it into materia. You should always be encouraged to use your best gear, there should NEVER be a downside to putting your best foot forward.
THAT is Final Fantasy. Not some stupid Oh well i have to choose between grinding materia and doing my best bull****.
Time to wake up and stop petitioning for medicore decisionmaking JUST BECAUSE.