@gummicorn I've moved your post to the Sims 4 general discussion section.
When you buy Sims 4 on Steam, you're required to link your Steam account to an Origin account. From then on, even if the Origin account also owns Sims 4, you'll be required to launch the game through Steam, with Origin running quetly in the background. In order to play through Origin again, you'd likey have to either refund the game on Steam, or otherwise remove it from your account; or unlink your accounts, which isn't always possible. Furthermore, you'd at least have to clear Origin's cache, but often this isn't enough—many people have to contact EA customer support to restore the Origin copies of their games.
@The_other_Rare There are several different ways that EA games are handled through Steam. It's always helpful to know the specifics of the particular game you're commenting on before asserting that it works a certain way or that there won't be consequences to having a copy in both platforms.
@eustacecs I'm not sure what you're asking. If you buy Sims 4 on Steam and want to install it, you'll need to link your Steam account to an Origin account before you can play. An existing account works fine, or at least it should and usually does.
