>>49463091PLA specifically sets up a reward system for each star, trainer cards don't. As you earn each star you unlock better mechanics, items, and recipes; it's truly a wonder that people might expect something unique for the final and most challenging star.
While past games did not reward you for stars specifically, even they often gave you unique decorations like paintings of your pokemon and trophies for completing the tasks that unlock the stars in the first place. Unlocking a unique outfit in PLA or a decoration for your house, or even something like rebranding the color of your pokedex book (similar to how Trainer cards change color) isn't asking for a lot. Anything more memorable than getting a handful of consumables you can find for yourself and certainly will not need at this point in the game.
