Tara wants to play a wizard. She can't cast magic, but that's fine, it's just a game. Tom and Jerry are both playing front-line melee of different classes. Jerry used to be a Marine and he can really describe it, Tom ... not so much. But hey, we have mechanics for that and as long as Tom can manage decent tactics we're okay. It's funny, Tom is playing a ranger even though Jerry would be the one who could describe all of the woodscraft. Christine wants to play a half-elven paladin of Corellon; she's a laid back agnostic from a family of them that probably never was to a religious service except for weddings and funerals. Still no problem - it's a fantasy game.
And then we have Harry. He just finished watching Ladyhawke (again), and he wants to play a glib, silver-tongued character. But our Harry is anything but a smooth talker. He's earnest and loyal, but never been good with words.
So what do you do? No one else needs to demonstrate actual skills of their characters - that's what the mechanics are there for. But everyone at the table can convince in character and the closest Harry will get is "I interject a bunch of witty remarks so they like me."
Do you let the mechanics and dice carry him, just like Tara's Fly spell? Do you convince Harry that other people's character concepts can come true but not his, even though the rules allow it? Would you just expect Harry not to ask to play something that so far our of his personal wheelhouse?
This is a made-up example, but how do you, at your table, handle this if it comes up? And the flip side - that player who likes to talk and is good at it but for this character picked CHR as their dump stat and didn't take any social skills.
the player describes what his character is attempting - the resolution process determines how successful. No need for the player to be good with the task in real life.
That applies for the cha 8 smooth talking player and the cha 16 social challenged player equally.
Some Gms put a lot more weight on the player's ability to do the thing than the character, to describe it in a way that seems "better at getting it done" (which requires more player knowledge of the task itself almost by default) means easier time in resolution.
i am not that kind of Gm for the most part.
i also tend to avoid "player riddles" tho so perhaps i am an odd duck.