I actually still use leves for alt jobs under lv40. I get sick of leveling using the same methods over and over, so I'm burned out on grinding through spamming the same dungeons, and with leves I can accomplish the goal for exp at my own pace.
I honestly wish they'd just make leves not be interrupted by duties, so there would be maybe some point in forming a leve party with my friend while waiting as dps, too.
And I just like any excuse to do open world content instead of more instanced stuff.