I keep on saving mine for the lvl 45+ Guild Leves.

And as Kahri said everyone would spam Leves if it werent for the allowance system, which means everyone would instantly get lvl 50 within everything thanks to that xD
Leve's are ment for that extra boost of exp that u want to get within any of the Hands, if u wanna lvl up gathering, crafting or maybe ur 2-7 job^^