FF1 for the GBA was far too easy with MP. To that end, it basically made the Black Mage much more useful, and made Knight, Ninja and Red Mage even more broken than they were before.

I think the main reason they kept the spell level system this time is because there charges per level cap is higher than 9, thus it's not considered to be "too hard" for some of today's hopelessly unskilled gamers who will give a game a poor review just because they sucked at it.