But, then TV Tropes happened.  I was on the WMG page for FFV, when I ran into this theory:

The game is Square's attempt at a Henshin Hero work.

Although the Job System is nothing new to Final Fantasy, FFV mixes up the format by having the jobs only activate in battle (as the out-of-battle Freelancer sprites are kept), thus we can conclude that the crystals serve as transformation trinkets. Other elements of the game that make it look sillier than other installments can also be attributed to this.

…Thank you, TV Tropes.  I now have a mental image of Bartz changing into his Dancer class Sailor Moon-style.   Complete with him shouting “WIND CRYSTAL POWER MAKE-UP!” before it starts.

Excuse me while I fix my brain.