It's not a punishment, it's just also not a mechanical reward. But it's preferable to making people play roles and jobs they don't enjoy lest they lack crucial parts of their abilities (provoke, swiftcast, blood for blood, quelling strikes, etc) - all of the FF14 jobs are designed to be complete on their own, so if you're leveling alternate jobs it's so that you can flex jobs or roles to fit different parties, not because you need an ability from Monk you don't get until level 46