Platitun / Questions and answers
Why not deal with the seller directly
You can — but then all you have left is trust. The money goes to the seller at once, there is nobody to dispute with, and no refund. The seller is in the same trouble: an accusation of non-delivery is impossible to disprove.
That is why passing contact details in questions and chat is forbidden, and trying to move a deal off the platform lowers the seller’s rating. Logins and passwords are allowed — those are the subject of the deal, not a way to escape it.
The marketplace commission pays for exactly this: a third party holding the money, and someone to sort it out when something goes wrong.