Not for playing.
In Mario 64 if you get all 120 stars you can find Yoshi. You can't ride Yoshi or anything silly like that, he gives you 99 lives, a totally meaningless gesture in a game which lets you save pretty much anywhere. This is, as one memorable wag used to repeatedly put it, a slap in the face.
I figured out what I was expecting. I was expecting free usage of caps. Go into any stage with any cap, and no timer. Transform into vanish cap Mario and be invisible forever. Listen to the metal cap music on loop for as long as you want. (So, you know, how power-ups worked in every other game in the series before this.) You already have all the stars. It's not like you can gain an unfair advantage by doing this.
It would just plain be fun.
But games aren't for playing.
At the time it was hard to work out what I was expecting because, frankly, I had worked it out. I was expecting disappointment. The game was foretold! In accordance with prophecy! The caps idea was buried almost before it was formed. Barely made the tiniest conscious ripple. However, I find it useful to contrast what should have happened with what actually happened, to help paint the outlines of what is actually happening and thus what is actually going wrong.
Bonus round: when you find Yoshi he jumps away with a truly epic jump, thus demonstrating that being able to ride him would have been extremely helpful...or it was a cutscene disrespecting its own world, "fuck videogames," as per usual.
Exception: Magicka. Exception: Minecraft.
Why is Minecraft so overwhelmingly popular? Because there's practically no other game that's actually a toy, made for fun. All the other games are a list of chores with pretty sounds and lights attached to "success," where "success" is wholly defined by the game developer, with no input from the player. ("Interactive medium" lol.)
Minecraft is a true sandbox, with, like, actual sand.
As with any sandbox it doesn't interest adults much because it's shallow. Even if you want to make a large pit, you can't, the sand only goes down so far.
Why won't the player roleplay in your world? Because it's obviously not game night, you've given them a list of chores.
Sure at least in an Elder Scrolls game you can go and do chores that aren't on the list, and maybe if you haven't tried chores like this 10,000X before they're certainly better than real-life chores. The spellslinging classes have the prettiest lights. Not as pretty as Metroid Prime's lights, but you can see they really aspired.
They're still ultimately chores.
You don't play the game, you work the game.
When "players" complain about World of Warcraft quests, they don't complain that they're literally a to-do list, they complain that the chores don't have fancy window-dressing. Culturally, the fetch ten rat pelts "quest" fits right in.
What if combat in your game was inherently enjoyable? Don't you realize "grinding" should be an engaging activity in an RPG? Imagine someone complaining that you had to throw balls at the hoop too many times in basketball. "I'm tired of taking pawns in chess. Can't you speed this up?" "This novel has too many scenes in it. Not to mention the words, my goodness."
They have to make them a Skinner box because the lever isn't a toy. Pressing it isn't fun (merely less work than other chores), the only rewarding thing about it is the reward. Of course players only care about getting loot so they can level up faster, or levelling up faster so they can get shinier loot. There's no actual "game" in your game, the point of a Skinner box is to press the lever harder and more often. No wonder Vampire Survivors, which tripled down on the levelling up and the flashing loot lights (and is cheap as balls) is so popular.
If you're going to make your "game" a series of chores, at least make them challenging chores so the "players" can learn something. Make the reward the satisfaction of a job well done, of a tall mountain conquered, not the satisfaction of mommy patting you on the head and teacher giving you a gold star.
I attribute this to general degeneracy. Democratic Man gonna Democrat. If you make games with good taste you offend the many, many, many "gamers" who have awful taste.
Imagine making a game where you plan to charge $500 because you plan to sell only to the smartest n%. Luxury gaming. And, because they have taste, you do in fact have to make the game nearly $500 good. Imagine how badly you would get ripped on social media.