I don't, honestly. I think progress is managed different way in the game and I feel that levels would push you more from exploring to grinding and hoarding. Starbound is not a RPG for me
I usually like RPG mechanics like character levelling, but Starbound isn't the type of game for it. The role and strengths of a character are defined through their equipment, which I think can work pretty well. It allows you to change your character to suit your needs.