They don't, because unlike Ubisoft, they're mostly a middleman. They run the marketplace for other game vendors and so they have reputation to uphold. However, Ubisoft is primarily a game developer, so there is a moral hazard of them screwing you.
We all hate middlemen but this shows why they're needed (in the absence of regulation).
We all hate middlemen but this shows why they're needed (in the absence of regulation).