BRAZILIAN_GODESS A game update doesn't delete saves on its own. It's possible your saves are still present but not read by the game, or that they've been pushed to cloud storage. Please see the first post of this thread for more information:
https://answers.ea.com/t5/PC/CURRENT-ISSUE-Sims-4-saves-user-content-disappearing-PC/td-p/12475370
If the saves themselves are truly gone, it's a system issue, or perhaps you installed the game itself in the same location as your user data, in which case an update could clear out everything not related to the game's program files. But it's not an inherent flaw with the update itself.